Human gingival fibroblasts rescue butyric acid-induced T-cell apoptosis

Gut-Bone Axis: A Non-Negligible Contributor to Periodontitis

Periodontitis is a polymicrobial infectious disease characterized by alveolar bone loss. Systemic diseases or local infections, such as diabetes, postmenopausal osteoporosis, obesity, and inflammatory bowel disease, promote the development and progression of periodontitis. Accumulating evidences have revealed the pivotal effects of gut microbiota on bone health via gut-alveolar-bone axis. Gut pathogens or metabolites may translocate to distant alveolar bone via circulation and regulate bone homeostasis. In addition, gut pathogens can induce aberrant gut immune responses and subsequent homing of immunocytes to distant organs, contributing to pathological bone loss. Gut microbial translocation also enhances systemic inflammation and induces trained myelopoiesis in the bone marrow, which potentially aggravates periodontitis. Furthermore, gut microbiota possibly affects bone health via regulating the production of hormone or hormone-like substances. In this review, we discussed the links between gut microbiota and periodontitis, with a particular focus on the underlying mechanisms of gut-bone axis by which systemic diseases or local infections contribute to the pathogenesis of periodontitis.

Effects of Short-Chain Fatty Acids on Human Oral Epithelial Cells and the Potential Impact on Periodontal Disease: A Systematic Review of In Vitro Studies

Short-chain fatty acids (SCFA), bacterial metabolites released from dental biofilm, are supposed to target the oral epithelium. There is, however, no consensus on how SCFA affect the oral epithelial cells. The objective of the present study was to systematically review the available in vitro evidence of the impact of SCFA on human oral epithelial cells in the context of periodontal disease. A comprehensive electronic search using five databases along with a grey literature search was performed. In vitro studies that evaluated the effects of SCFA on human oral epithelial cells were eligible for inclusion. Risk of bias was assessed by the University of Bristol's tool for assessing risk of bias in cell culture studies. Certainty in cumulative evidence was evaluated using GRADE criteria (grading of recommendations assessment, development, and evaluation). Of 3591 records identified, 10 were eligible for inclusion. A meta-analysis was not possible due to the heterogeneity between the studies. The risk of bias across the studies was considered "serious" due to the presence of methodological biases. Despite these limitations, this review showed that SCFA negatively affect the viability of oral epithelial cells by activating a series of cellular events that includes apoptosis, autophagy, and pyroptosis. SCFA impair the integrity and presumably the transmigration of leucocytes through the epithelial layer by changing junctional and adhesion protein expression, respectively. SCFA also affect the expression of chemokines and cytokines in oral epithelial cells. Future research needs to identify the underlying signaling cascades and to translate the in vitro findings into preclinical models.

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.

Deletion of from Streptococcus pyogenes. Results in Hypervirulence in a Mouse Model of Sepsis and is LuxS Independent

Group A Streptococcus (GAS) is a Gram-positive human pathogen that causes a variety of diseases ranging from pharyngitis to life-threatening streptococcal toxic shock syndrome. Recently, several global gene expression analyses have yielded extensive new information regarding the regulation of genes encoding known and putative virulence factors in GAS. A microarray analysis found that transcription of the GAS gene M5005_Spy_1343 was significantly increased in response to interaction with human polymorphonuclear leukocytes. M5005_Spy_1343 is predicted to encode a member of the LysR family of transcriptional regulators and is located upstream of a putative operon containing six genes. Five of these genes have sequence similarity to genes involved in short-chain fatty acid metabolism, whereas the sixth gene (luxS) is found in many bacterial species and is involved in quorum sensing. Unexpectedly, inactivation of the M5005_Spy_1343 gene resulted in hypervirulence in an intraperitoneal mouse model of infection. Increased virulence was not due to changes in luxS gene expression. We postulate that short-chain fatty acid metabolism is involved in GAS pathogenesis.

Activity of 25-hydroxylase in human gingival fibroblasts and periodontal ligament cells

Background

We previously demonstrated that 25-hydroxyvitamin D₃ concentrations in gingival crevicular fluid are 300 times higher than those in the plasma of patients with aggressive periodontitis. Here we explored whether 25-hydroxyvitamin D₃ can be synthesized by periodontal soft tissue cells. We also investigated which of the two main kinds of hydroxylases, CYP27A1 and CYP2R1, is the key 25-hydroxylase in periodontal soft tissue cells.

Methodology/Principal Findings

Primary cultures of human gingival fibroblasts and periodontal ligament cells from 5 individual donors were established. CYP27A1 mRNA, CYP2R1 mRNA and CYP27A1 protein were detected in human gingival fibroblasts and periodontal ligament cells, whereas CYP2R1 protein was not. After incubation with the 25-hydroxylase substrate vitamin D₃, human gingival fibroblasts and periodontal ligament cells generated detectable 25-hydroxyvitamin D₃ that resulted in the production of 1α,25-dihydroxyvitamin D₃. Specific knockdown of CYP27A1 in human gingival fibroblasts and periodontal ligament cells using siRNA resulted in a significant reduction in both 25-hydroxyvitamin D₃ and 1α,25-dihydroxyvitamin D₃ production. Knockdown of CYP2R1 did not significantly influence 25-hydroxyvitamin D₃ synthesis. Sodium butyrate did not influence significantly CYP27A1 mRNA expression; however, interleukin-1β and Porphyromonas gingivalis lipopolysaccharide strongly induced CYP27A1 mRNA expression in human gingival fibroblasts and periodontal ligament cells.

Conclusions

The activity of 25-hydroxylase was verified in human gingival fibroblasts and periodontal ligament cells, and CYP27A1 was identified as the key 25-hydroxylase in these cells.

Butyric acid induces apoptosis in both human monocytes and lymphocytes equivalently

Short-chain fatty acids (SCFAs) are metabolites from anaerobic periodontopathic bacteria that induce apoptosis in immune cells such as lymphocytes, monocytes and macrophages. However, it remains unclear if SCFAs from pathogens induce apoptosis in monocytes/macrophages similarly with lymphocytes. This study investigated whether SCFAs-induced apoptosis is equal among the immunoregulatory cells. Cell apoptosis of the employed human cells was evaluated after treatment with culture supernatants from various periodontopathic bacteria or sodium butyrate. Apoptosis and viability were determined by detection of DNA fragmentation and using an MTS assay kit, respectively. Porphyromonas gingivalis and Fusobacterium nucleatum culture filtrates strongly induced apoptosis whereas Prevotella nigrescens and Prevotella intermedia culture filtrates failed to induce apoptosis in the THP-1 and U937 human monocyte and macrophage cell lines. Healthy gingival fibroblasts and oral epithelial cells were resistant to all the culture filtrates. Gas-liquid chromatography detected butyric acid in P. gingivalis (21.0-34.0 mM) and F. nucleatum (36.0 mM) in culture filtrates, whereas, only trace levels were seen in P. nigrescens and P. intermedia. These results suggest that butyric acid produced by periodontopathic bacteria severely damages immunoregulatory cells in a consistent manner and, likewise, could be involved in mediating periodontal chronic inflammation.

Characterization of the autocrine/paracrine function of vitamin D in human gingival fibroblasts and periodontal ligament cells

BACKGROUND

We previously demonstrated that 25-hydroxyvitamin D(3), the precursor of 1α,25-dihydroxyvitamin D(3), is abundant around periodontal soft tissues. Here we investigate whether 25-hydroxyvitamin D(3) is converted to 1α,25-dihydroxyvitamin D(3) in periodontal soft tissue cells and explore the possibility of an autocrine/paracrine function of 1α,25-dihydroxyvitamin D(3) in periodontal soft tissue cells.

METHODOLOGY/PRINCIPAL FINDINGS

We established primary cultures of human gingival fibroblasts and human periodontal ligament cells from 5 individual donors. We demonstrated that 1α-hydroxylase was expressed in human gingival fibroblasts and periodontal ligament cells, as was cubilin. After incubation with the 1α-hydroxylase substrate 25-hydroxyvitamin D(3), human gingival fibroblasts and periodontal ligament cells generated detectable 1α,25-dihydroxyvitamin D(3) that resulted in an up-regulation of CYP24A1 and RANKL mRNA. A specific knockdown of 1α-hydroxylase in human gingival fibroblasts and periodontal ligament cells using siRNA resulted in a significant reduction in both 1α,25-dihydroxyvitamin D(3) production and mRNA expression of CYP24A1 and RANKL. The classical renal regulators of 1α-hydroxylase (parathyroid hormone, calcium and 1α,25-dihydroxyvitamin D(3)) and Porphyromonas gingivalis lipopolysaccharide did not influence 1α-hydroxylase expression significantly, however, interleukin-1β and sodium butyrate strongly induced 1α-hydroxylase expression in human gingival fibroblasts and periodontal ligament cells.

CONCLUSIONS/SIGNIFICANCE

In this study, the expression, activity and functionality of 1α-hydroxylase were detected in human gingival fibroblasts and periodontal ligament cells, raising the possibility that vitamin D acts in an autocrine/paracrine manner in these cells.

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.

Sodium butyrate induces the production of cyclooxygenases and prostaglandin E₂ in ROS 17/2.8 osteoblastic cells

OBJECTIVE

Sodium butyrate (butyric acid; BA) is a major metabolic by-product of the anaerobic periodontopathic bacteria present in subgingival plaque. We examined the effects of BA and/or indomethacin on cell proliferation, the expression of cyclooxygenases (COXs), prostaglandin (PG) receptors (EP1-4), extracellular matrix proteins, such as type I collagen and osteopontin, and PGE(2) production, using ROS17/2.8 cells as osteoblasts.

METHODS

The rat clonal cell line ROS 17/2.8 was cultured with 0, 10(-5), 10(-4), and 10(-3)M BA in the presence or absence of 0.5 μM indomethacin, for up to 7 days. The expression of COX-1, COX-2, EP1, EP2, EP3, EP4, type I collagen, and osteopontin was examined at the mRNA and protein levels using real-time PCR and Western blotting, respectively. The amount of PGE(2) in the culture medium was measured by ELISA.

RESULTS

Proliferation of ROS 17/2.8 cells was not affected by the addition of BA. However, PGE(2) production and the expression of COX-1 and COX-2 increased with the addition of BA. In contrast, indomethacin, an inhibitor of COX, blocked the stimulatory effect of BA. Furthermore, EP2 expression increased with BA treatment, whereas EP1 expression was not affected and the expression of EP3 and EP4 was not detected. The addition of BA also increased the expression of type I collagen and osteopontin. Indomethacin blocked about 50% of the stimulatory effect of BA on type I collagen, whereas it did not block the effect on osteopontin.

CONCLUSIONS

These results suggest that BA induces PGE(2) production by increasing the expression of COX-1 and COX-2 in osteoblasts, and that an autocrine action of the produced PGE(2), via EP1 or BA-induced EP2, is related to an increase in type I collagen expression by BA.

The role of Desulfovibrio desulfuricans lipopolysaccharides in modulation of periodontal inflammation through stimulation of human gingival fibroblasts

OBJECTIVE

Periodontitis is a destructive disease which is likely to be the result of the activities of different microbial complexes. Recently, sulphate-reducing bacteria (SRB) have been detected in the oral cavity, and they have been found to be common inhabitants of sites showing periodontal destruction. The aim of study was to evaluate the influence of endotoxins of Desulfovibrio desulfuricans bacteria on human gingival fibroblast HGF-1 line.

METHODS

The immunological response of gingival fibroblasts was evaluated by determination of their IL-6 and IL-8 secretion upon treatment with D. desulfuricans intestinal and type strain LPS, sodium butyrate (NaB) and IL-1beta. The amounts of cytokines were estimated by ELISA immunoassay. The influence of LPS and NaB on fibroblast proliferation was determined using the CyQUANT Cell Proliferation Assay Kit.

RESULTS

No significant growth inhibition of cells exposed to LPS was observed, except for the culture growing in the presence of intestinal strain endotoxin at the highest concentration (100 microg/ml). The secretion of IL-6 and IL-8 by fibroblasts was increased by D. desulfuricans endotoxins. Cells stimulated with proinflammatory cytokine 1L-1beta showed very high levels of both cytokines secretion. The release of IL-6 and IL-8 by cells in response to LPS and 1L-1beta was modulated by butyric acid.

CONCLUSIONS

The observed response of gingival fibroblasts to stimulation by endotoxin suggests that D. desulfuricans can be involved in the pathogenesis of periodontitis. Moreover, butyrate present in the oral cavity seems to have immunoregulatory effect on cytokine production by gingival fibroblasts under physiological conditions and during microbe-induced inflammation.

Increased susceptibility to tumor necrosis factor-alpha in butyric acid-induced apoptosis is caused by downregulation of cFLIP expression in Jurkat T cells

Butyric acid is one of the major extracellular metabolites of periodontopathic Gram-negative bacteria. We previously demonstrated that butyric acid induced apoptosis in human T cells. In the present study, we examined the interaction between butyric acid and TNF-alpha in Jurkat T-cell apoptosis. Simultaneous treatment with TNF-alpha enhanced butyric acid-induced apoptosis by promoting caspase activity more than was achieved by either reagent alone. We examined which genes were associated with the increased susceptibility to TNF-alpha caused by butyric acid, and revealed that expression of cFLIP decreased with increased concentrations of butyric acid. Furthermore, exogenous expression of cFLIP protein suppressed the enhancing effect by TNF-alpha in the apoptosis. These results suggest that butyric acid downregulates cFLIP expression and increases the susceptibility to TNF-alpha by activating caspases via the death receptor signal.

Sodium butyrate stimulates mineralized nodule formation and osteoprotegerin expression by human osteoblasts

OBJECTIVE

Butyric acid (sodium butyrate; BA) is a major metabolic by-product of main periodontopathic bacteria present in subgingival plaque. In the present study, we examined the effects of BA on cell proliferation, alkaline phosphatase (ALPase) activity, mineralized nodule formation, extracellular matrix protein expression, macrophage colony-stimulating factor (M-CSF), and osteoprotegerin (OPG) in normal human osteoblasts.

METHODS

The cells were cultured with 0, 10(-8), 10(-6) or 10(-4)M BA for up to 12 days. Mineralized nodule formation was detected by alizarin red staining, and the calcium content in mineralized nodules was determined using a calcium assay kit. The gene and protein expression levels for type I collagen, bone sialoprotein (BSP), osteopontin (OPN), M-CSF, and OPG were examined using real-time PCR and ELISA, respectively.

RESULTS

Mineralized nodule formation and the calcium content of mineralized nodules were increased by BA in a dose-dependent manner. Cell proliferation and ALPase activity were not affected by the addition of BA. Following the addition of 10(-4)M BA, the expression levels of BSP, OPN, and OPG increased, whereas the expression levels of type I collagen and M-CSF were not markedly affected.

CONCLUSION

These results suggest that BA stimulates bone formation by increasing the production of BSP and OPN, whereas it suppresses osteoclast differentiation by increasing the production of OPG by human osteoblasts.

Butyric Acid Induces Apoptosis in Inflamed Fibroblasts

Butyric acid, an extracellular metabolite from periodontopathic bacteria, induces apoptosis in murine and human T- and B-cells, whereas intact gingival fibroblasts isolated from healthy humans are resistant to butyric-acid-induced apoptosis. We examined the susceptibility of inflamed gingival fibroblasts isolated from adult persons with periodontitis to butyric-acid-induced apoptosis. Butyric acid significantly suppressed the viability of inflamed gingival fibroblasts and induced apoptosis in a dose-dependent manner. The incubation of inflamed gingival fibroblasts with butyric acid induced DNA fragmentation and apoptotic changes such as chromatin condensation, hypodiploid nuclei, and mitochondrial injury. Furthermore, butyric-acid-induced apoptosis in inflamed gingival fibroblasts was reduced by caspase-3/7, -6, -8, and -9 inhibitors. Thus, inflamed gingival fibroblasts from adult persons with periodontitis appear to be highly susceptible to mitochondria- and caspase-dependent apoptosis induced by butyric acid, compared with healthy gingival fibroblasts.

The role of IL-6 in inhibition of lymphocyte apoptosis by mesenchymal stem cells

Mesenchymal stem cells (MSCs) are widely distributed throughout the body. Despite intensive studies on the immunosuppressive effect of MSCs, little is known about whether MSCs affect lymphocyte apoptosis. We investigated the effect of MSCs on the spontaneous death of lymphocytes and found that MSCs inhibit the apoptosis of splenocytes and thymocytes as well as purified T and B cells. The protective effect of MSCs was absent when lymphocytes were not in contact with MSCs, indicating that the anti-apoptotic effect is exerted through direct interaction between MSCs and lymphocytes. Interestingly, this anti-apoptotic effect could be inhibited by neutralization of IL-6. Consequently, we found that the expression of IL-6 by MSCs was augmented by contact with lymphocytes. Taken together, these results demonstrate that IL-6 plays an important role in the inhibition of lymphocyte apoptosis by MSCs.

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.

Transforming growth factor-beta stimulates Interleukin-11 production by human periodontal ligament and gingival fibroblasts

BACKGROUND

Transforming growth factor (TGF)-beta is a potent multifunctional polypeptide, abundant in the bone matrix. Interleukin (IL)-11 is a pleiotropic cytokine with effects on multiple cell types. The present study was performed to evaluate the regulatory effects of TGF-beta on IL-11 production by human periodontal ligament cells (PDL) and human gingival fibroblasts (HGF).

MATERIAL AND METHODS

The expression of TGF-beta receptor in PDL and HGF were observed using flow cytometry. PDL and HGF were stimulated with TGF-beta with or without protein kinase C (PKC) inhibitors and activator. IL-11, bone morphogenetic protein-2 (BMP-2) and TGF-beta mRNA expression was quantified by real-time polymerase chain reaction (PCR). IL-11 production was measured using enzyme-linked immunosorbent assay.

RESULTS

PDL and HGF expressed both TGF-beta receptor I and TGF-beta receptor II on the cell surfaces. IL-11 mRNA expression and IL-11 production were augmented by TGF-beta in both PDL and HGF, with higher values in PDL. PKC inhibitors partially suppressed TGF-beta-induced IL-11 production in PDL and HGF, whereas activator enhanced it. TGF-beta mRNA and BMP-2 mRNA expression were up-regulated by TGF-beta in PDL.

CONCLUSION

These results suggest that PDL produce IL-11 in response to TGF-beta.

Intestinal Fibroblast-Derived IL-10 Increases Survival of Mucosal T Cells by Inhibiting Growth Factor Deprivation- and Fas-Mediated Apoptosis

Mucosal T cells are essential to immune tolerance in the intestine, an organ constantly exposed to large amounts of dietary and bacterial Ags. We investigated whether local fibroblasts affect mucosal T cell survival, which is critical for maintenance of immune tolerance. Coculture with autologous fibroblasts significantly increased viability of mucosal T cells by inhibiting IL-2 deprivation- and Fas-mediated apoptosis, an effect that was both contact- and secreted product-dependent. Investigation of anti-apoptotic factors in the fibroblast-conditioned medium (FCM) revealed the presence of IL-10 and PGE2, but not IFN-beta, IL-2, or IL-15. Although recombinant IFN-beta, but not PGE2, effectively prevented T cell apoptosis, neutralizing Ab studies showed that only IL-10 blockade significantly increased T cells apoptosis, whereas neutralizing IFN-beta or IFN-alpha failed to inhibit the anti-apoptotic effect of FCM. To confirm that fibroblast-derived IL-10 was responsible for preserving mucosal T cell viability, IL-10 mRNA was demonstrated in fibroblasts by Southern blotting and RT-PCR. When FCM was submitted to HPLC fractionation, only the peak matching rIL-10 contained the anti-apoptotic activity, and this was eliminated by treatment with an IL-10-neutralizing Ab. Finally, when fibroblasts were transiently transfected with IL-10 antisense oligonucleotides, the conditioned medium lost its T cell anti-apoptotic effect, whereas medium from fibroblasts transfected with IFN-beta antisense oligonucleotides displayed the same anti-apoptotic activity of medium from untransfected fibroblasts. These results indicate that local fibroblast-derived IL-10 is critically involved in the survival of mucosal T cells, underscoring the crucial importance of studying organ-specific cells and products to define the mechanisms of immune homeostasis in specialized tissue microenvironments like the intestinal mucosa.