Compromised inflammatory cytokine response to P. gingivalis LPS by fibroblasts from inflamed human gingiva

Cell-Type-Specific ROS–AKT/mTOR–Autophagy Interplay—Should It Be Addressed in Periimplantitis?

Periimplantitis represents an inflammatory disease of the soft and hard tissues surrounding the osseointegrated dental implant, triggering progressive damage to the alveolar bone. Cumulative data have revealed that periimplantitis plays a crucial part in implant failure. Due to the strategic roles of autophagy and its upstream coordinator, the AKT/mTOR pathway, in inflammatory responses, the crosstalk between them in the context of periimplantitis should become a key research target, as it opens up an area of interesting data with clinical significance. Therefore, in this article, we aimed to briefly review the existing data concerning the complex roles played by ROS in the interplay between the AKT/mTOR signaling pathway and autophagy in periimplantitis, in each of the main cell types involved in periimplantitis pathogenesis and evolution. Knowing how to modulate specifically the autophagic machinery in each of the cellular types involved in the healing and osseointegration steps post implant surgery can help the clinician to make the most appropriate post-surgery decisions. These decisions might be crucial in order to prevent the occurrence of periimplantitis and ensure the proper conditions for effective osseointegration, depending on patients’ clinical particularities.

Anti-inflammatory effects of hesperidin on human gingival fibroblasts stimulated by lipopolysaccharide of Porphyromonas gingivalis in vitro

Periodontal disease is an inflammatory disease caused by periodontopathogenic bacteria, the inflammatory response generated against them, and host factors. Furthermore, environmental factors can lead to disease progression. Using lipopolysaccharide (LPS)-stimulated human gingival fibroblast (HGF), this study investigated the bioactivity of HGF after exposure to hesperidin (Hesp) and the anti-inflammatory activity of Hesp against early periodontitis. HGF were cultured in Dulbecco's modified Eagle's medium containing 15% fetal bovine serum. They were exposed to LPS for 6 h, followed by Hesp (1, 10, 30, and 50 µM) exposure for 4 h. Cell proliferation was evaluated using reduction staining with alamerBlue™. Inflammatory cytokines [interleukin (IL)-6 and IL-8] and Toll-like receptor 4 (TLR4) levels were assessed using reverse transcription quantitative polymerase chain reaction. Hesp 50 µM + LPS inhibited cell proliferation. The Hesp exposure group inhibited the expression of IL-8 and IL-6. No significant difference in TLR4 expression was observed. Hesp significantly suppressed IL-6 and IL-8 expression by inhibiting downstream signaling without inhibiting TLR4 activation.

Circ_0099630 knockdown alleviates lipopolysaccharide-induced injuries of human periodontal ligament cells through the inhibition of TLR4 by releasing miR-409-3p

BACKGROUND

Periodontitis triggers tooth loss and affects the health of population worldwide. Emerging evidence hints that circular RNAs (circRNAs) are involved in various diseases, including periodontitis. This study aimed to investigate the role of circ_0099630 in the progression of periodontitis.

METHODS

Periodontitis cell model was constructed by treating human periodontal ligament cells (HPDLCs) with lipopolysaccharide (LPS). Quantitative real-time PCR was used to analyze the expression of circ_0099630, microRNA-409-3p (miR-409-3p) and toll-like receptor 4 (TLR4) mRNA. Western blot was used for detecting protein levels of TLR4, cleaved-caspase 3, Bcl-2, CyclinD1 and NF-κB signaling markers. For function analyses, cell proliferation was assessed by CCK-8 assay and EdU assay. The releases of pro-inflammation factors were monitored by ELISA kits. The potential relationship between miR-409-3p and circ_0099630 or TLR4 was verified by dual-luciferase reporter assay, RIP assay and pull-down assay.

RESULTS

The expression of circ_0099630 and TLR4 was elevated in periodontitis patients and LPS-treated HPDLCs. LPS induced HPDLC proliferation inhibition, apoptosis and inflammatory responses, while circ_0099630 knockdown or TLR4 knockdown alleviated these injuries. Besides, TLR4 overexpression reversed the inhibitory effect of circ_0099630 knockdown on LPS-induced HPDLC injuries. Mechanism analysis showed that circ_0099630 positively regulated TLR4 expression by acting as miR-409-3p sponge. MiR-409-3p restoration largely ameliorated LPS-induced HPDLC injuries by depleting TLR4. Moreover, LPS activated the NF-κB signaling pathway, while circ_0099630 knockdown inhibited the activity of NF-κB signaling via the miR-409-3p/TLR4 axis.

CONCLUSION

Circ_0099630 knockdown relieved LPS-induced HPDLC injury by miR-409-3p/TLR4 axis, suggesting that circ_0099630 might be a potential target for periodontitis treatment.

Bioinformatic Analysis of the CXCR2 Ligands in Cancer Processes

Human CXCR2 has seven ligands, i.e., CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL7, and CXCL8/IL-8-chemokines with nearly identical properties. However, no available study has compared the contribution of all CXCR2 ligands to cancer progression. That is why, in this study, we conducted a bioinformatic analysis using the GEPIA, UALCAN, and TIMER2.0 databases to investigate the role of CXCR2 ligands in 31 different types of cancer, including glioblastoma, melanoma, and colon, esophageal, gastric, kidney, liver, lung, ovarian, pancreatic, and prostate cancer. We focused on the differences in the regulation of expression (using the Tfsitescan and miRDB databases) and analyzed mutation types in CXCR2 ligand genes in cancers (using the cBioPortal). The data showed that the effect of CXCR2 ligands on prognosis depends on the type of cancer. CXCR2 ligands were associated with EMT, angiogenesis, recruiting neutrophils to the tumor microenvironment, and the count of M1 macrophages. The regulation of the expression of each CXCR2 ligand was different and, thus, each analyzed chemokine may have a different function in cancer processes. Our findings suggest that each type of cancer has a unique pattern of CXCR2 ligand involvement in cancer progression, with each ligand having a unique regulation of expression.

Silibinin alleviates inflammation-induced bone loss by modulating biological interaction between human gingival fibroblasts and monocytes

BACKGROUND

Silibinin has shown various pharmacological effects that could be attributed to its antioxidant, anti-inflammatory, and immunoregulatory properties. However, the therapeutic potential of silibinin for periodontitis has not been investigated.

METHODS

The therapeutic effects of silibinin in ligation-induced experimental periodontitis were investigated using biochemical, histological, and immunohistochemical methods. The effects of silibinin on the osteoclastogenesis of RAW264.7 cells were investigated using TRAP staining, quantitative polymerase chain reaction (qPCR), pit formation, and immunoblotting. Moreover, its effects on inflammatory cytokine production, RANKL expression, and oxidative stress in lipopolysaccharide (LPS)-stimulated human gingival fibroblasts (HGFs) were evaluated using qPCR and flow cytometry. A coculture system was established to elucidate the effects of silibinin on the crosstalk between LPS-stimulated HGFs and undifferentiated monocytes.

RESULTS

Silibinin significantly reduced the alveolar bone loss, decreased the gingival inflammation and RANKL expression, and decreased the RANKL/osteoprotegerin ratio in gingival tissues in experimental periodontitis. The in vitro results showed that silibinin inhibited RANKL-induced osteoclast differentiation and function of RAW264.7 cells and suppressed RANKL-induced nuclear factor of activated T cells 1 (NFATc1) induction and translocation through the nuclear factor-κB and mitogen-activated protein kinase signaling pathways. Silibinin decreased the inflammatory cytokine level and oxidative stress production in LPS-stimulated HGFs; significantly suppressed membrane-bound RANKL expression on LPS-stimulated HGFs; and significantly disrupted TRAP+ cell differentiation in the coculture system.

CONCLUSIONS

Silibinin effectively inhibits inflammation-induced bone loss in experimental periodontitis based on the regulation of stimulated HGFs by inhibiting the expression of inflammatory and osteoclastogenic mediators. Collectively, targeting the inflamed HGF resolution that mediates osteogenesis may use silibinin as a potential drug-repurposing candidate for modulating alveolar bone destruction in periodontitis.

SUMMARY

Silibinin effectively inhibits inflammation-induced bone loss in experimental periodontitis based on the regulation of stimulated HGFs by inhibiting the expression of inflammatory and osteoclastogenic mediators.

Free titanium particles and P. gingivalis lipopolysaccharide create a potentially synergistical effect in a periimplantitis model

OBJECTIVE

Our aim was to examine the effect of titanium particles and lipopolysaccharide (LPS) from P. gingivalis on the inflammatory profile expression of human gingival fibroblasts (hGFs), cultured on rough titanium discs, in an in vitro peri-implantitis simulation.

DESIGN

Human gingival fibroblasts cultured on SLA and TCP surfaces were challenged with LPS, titanium particles or both. At 24, 48 and 72 h after treatment, MTT assay was performed to assess cell proliferation. FDA/PI staining was performed for the same time periods, in order to evaluate cell viability/apoptosis. At 5 and 7 days after the treatment, qPCR was performed to assess gene expressions of IL-6, IL-8 and COL1A1, as well as SEM on titanium discs.

RESULTS

All groups presented a significant increase of their population between the time periods of examination. Regarding the interleukin gene expression, the combination of LPS and particles significantly increased the levels of Interleukin-8. Treatment with LPS and particles also induced a significant increase of Interleukin-6 and collagen. FDA/PI microscopy has revealed several apoptotic cells in the treatment groups. SEM micrographs have shown the difficulty of hGFs to adhere on rough surfaces.

CONCLUSIONS

The combination of titanium particles and LPS significantly upregulated the expression of IL-6, IL-8 and Col-1a. It appears that particles may arouse similar reactions to the endotoxin, while synergistically intensifying it.

Cathepsins in oral diseases: mechanisms and therapeutic implications

Cathepsins are a type of lysosomal globulin hydrolase and are crucial for many physiological processes, including the resorption of bone matrix, innate immunity, apoptosis, proliferation, metastasis, autophagy, and angiogenesis. Findings regarding their functions in human physiological processes and disorders have drawn extensive attention. In this review, we will focus on the relationship between cathepsins and oral diseases. We highlight the structural and functional properties of cathepsins related to oral diseases, as well as the regulatory mechanisms in tissue and cells and their therapeutic uses. Elucidating the associated mechanism between cathepsins and oral diseases is thought to be a promising strategy for the treatment of oral diseases and may be a starting point for further studies at the molecular level.

The Role of Gingival Fibroblasts in the Pathogenesis of Periodontitis

Gingival fibroblasts (GFs) are essential components of the periodontium, which are responsible for the maintenance of tissue structure and integrity. However, the physiological role of GFs is not restricted to the production and remodeling of the extracellular matrix. GFs also act as sentinel cells that modulate the immune response to oral pathogens invading the gingival tissue. As an important "nonclassical" component of the innate immune system, GFs respond to bacteria and damage-related signals by producing cytokines, chemokines, and other inflammatory mediators. Although the activation of GFs supports the elimination of invading bacteria and the resolution of inflammation, their uncontrolled or excessive activation may promote inflammation and bone destruction. This occurs in periodontitis, a chronic inflammatory disease of the periodontium initiated and sustained by dysbiosis. In the inflamed gingival tissue, GFs acquire imprinted proinflammatory phenotypes that promote the growth of inflammophilic pathogens, stimulate osteoclastogenesis, and contribute to the chronicity of inflammation. In this review, we discuss the biological functions of GFs in healthy and inflamed gingival tissue, highlighting recent studies that provide insight into their role in the pathogenesis of periodontal diseases. We also draw parallels with the recently discovered fibroblast populations identified in other tissues and their roles in health and disease. This knowledge should be used in future studies to discover more about the role of GFs in periodontal diseases, especially chronic periodontitis, and to identify therapeutic strategies targeting their pathological interactions with oral pathogens and the immune system.

Porphyromonas gingivalis-induced periodontitis could contribute to cognitive impairment in Sprague–Dawley rats via the P38 MAPK signaling pathway

Background

Periodontitis is one of the most common oral diseases and has been shown to be a risk factor for systemic diseases. Our aim was to investigate the relationship between periodontitis and cognitive impairment and to explore the role of the P38 MAPK signaling pathway in this process.

Methods

We established a periodontitis model by ligating the first molars of SD rats with silk thread and injecting Porphyromonas gingivalis (P. gingivalis) or P. gingivalis plus the P38 MAPK inhibitor SB203580 at the same time for ten weeks. We assessed alveolar bone resorption and spatial learning and memory using microcomputed tomography and the Morris water maze test, respectively. We used transcriptome sequencing to explore the genetic differences between the groups. The gingival tissue, peripheral blood and hippocampal tissue were assessed for the cytokines TNF-α, IL-1β, IL-6, IL-8 and C reactive protein (CRP) with enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT–PCR). We observed the presence of P. gingivalis in the hippocampus of rats by paraffin-fluorescence in situ hybridization (FISH). We determined the activation of microglia by immunofluorescence. Finally, Western blot analysis was employed to determine the expression of amyloid precursor protein (APP), β-site APP-cleaving enzyme 1 (BACE1) and P38MAPK pathway activation.

Results

We demonstrated that silk ligature-induced periodontitis plus injection of P. gingivalis into subgingival tissue could lead to memory and cognitive impairment. Transcriptome sequencing results suggested that there were neurodegenerative diseases in the P. gingivalis group, and the MWM test showed that periodontitis reduced the spatial learning and memory ability of mild cognitive impairment (MCI) model rats. We found high levels of inflammatory factors (TNF-α, IL-1β, IL-6, and IL-8) and CRP in the gingiva, peripheral blood and hippocampus, and the expression of APP and BACE1 was upregulated, as was the P38 MAPK pathway activation. Activated microglia and the presence of P. gingivalis were also found in the hippocampus. P38 MAPK inhibitors mitigated all of these changes.

Conclusion

Our findings strongly suggest that topical application of P. gingivalis increases the inflammatory burden in the peripheral and central nervous systems (CNS) and that neuroinflammation induced by activation of P38 MAPK leads to impaired learning and memory in SD rats. It can also modulate APP processing. Therefore, P38 MAPK may serve as a linking pathway between periodontitis and cognitive impairment.

Hexokinase 2-mediated glycolysis supports inflammatory responses to Porphyromonas gingivalis in gingival fibroblasts

BACKGROUND

When infected with Porphyromonas gingivalis, gingival fibroblasts undergo metabolic reprogramming, and rely on aerobic glycolysis rather than oxidative phosphorylation for rapid energy replenishment. Hexokinases (HKs) are catalysts for glucose metabolism, and HK2 constitutes the major HK inducible isoform. The objective of this study is to determine whether HK2-mediated glycolysis promotes inflammatory responses in inflamed gingiva.

METHODS

Levels of glycolysis-related genes were assessed in normal and inflamed gingiva. Human gingival fibroblasts were harvested and infected with Porphyromonas gingivalis in order to mimic periodontal inflammation. 2-deoxy-d-glucose, an analogue of glucose, was used to block HK2-mediated glycolysis, while small interfering RNA was used to knock down HK2 expression. The mRNA and protein levels of genes were analyzed by real-time quantitative PCR and western blotting, respectively. HK2 activity and lactate production were assessed by ELISA. Cell proliferation was assessed by confocal microscopy. The generation of reactive oxygen species was assessed by flow cytometry.

RESULTS

Elevated expression of HK2 and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 was observed in the inflamed gingiva. P. gingivalis infection was shown to promote glycolysis in human gingival fibroblasts, as evidenced by increased gene transcription of HK2 and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3, cell glucose consumption, and HK2 activity. Inhibition and knockdown of HK2 resulted in reduced cytokine production, cell proliferation, and reactive oxygen species generation. Furthermore, P. gingivalis infection activated the hypoxia-inducible factor-1α signaling pathway, thus promoting HK2-mediated glycolysis and proinflammatory responses.

CONCLUSIONS

HK2-mediated glycolysis promotes inflammatory responses in gingival tissues, and therefore glycolysis can be targeted in order to inhibit the progression of periodontal inflammation.

Biological Roles of Fibroblasts in Periodontal Diseases

Periodontal diseases include periodontitis and gingival overgrowth. Periodontitis is a bacterial infectious disease, and its pathological cascade is regulated by many inflammatory cytokines secreted by immune or tissue cells, such as interleukin-6. In contrast, gingival overgrowth develops as a side effect of specific drugs, such as immunosuppressants, anticonvulsants, and calcium channel blockers. Human gingival fibroblasts (HGFs) are the most abundant cells in gingival connective tissue, and human periodontal ligament fibroblasts (HPLFs) are located between the teeth and alveolar bone. HGFs and HPLFs are both crucial for the remodeling and homeostasis of periodontal tissue, and their roles in the pathogenesis of periodontal diseases have been examined for 25 years. Various responses by HGFs or HPLFs contribute to the progression of periodontal diseases. This review summarizes the biological effects of HGFs and HPLFs on the pathogenesis of periodontal diseases.

HSP90AA1 promotes the inflammation in human gingival fibroblasts induced by Porphyromonas gingivalis lipopolysaccharide via regulating of autophagy

BACKGROUND

Peri-implantitis of tooth seriously affects the life quality of patients. This study aimed to investigate the role of HSP90AA1 in the inflammatory of human gingival fibroblasts (HGFs) induced by porphyromonas gingivalis lipopolysaccharide (Pg-LPS), and to provide a potential therapeutic target for clinical treatment of peri-implantitis.

METHODS

Pg-LPS (0.1, 1, 10 μg/mL) was used to construct the inflammatory model of HGFs to evaluate the effect of Pg-LPS on HGFs. Then HSP90AA1-siRNA was transfected to construct HSP90AA1 low expression HGFs cell line, and 3-MA was also added. After that, cell viability, apoptosis, the contents of inflammatory cytokines were detected by CCK-8, flow cytometry and ELISA assay, respectively. Intracellular ROS, the expressions of HSP90α, HSP90β were detected by immunofluorescence. The levels of HSP90AA1, p-NF-κB p65/NF-κB p65, LC3 II/I, ATG5, Beclin-1 and TLR protein were detected by western blot.

RESULTS

Pg-LPS treatment didn't affect the viability of HGFs cells, but induced the cell apoptosis and ROS generation, increased the contents of IL-1β, IL-6, TNF-α, and the protein expressions of HSP90AA1, p-NF-κBp65/NF-κBp65, LC3II/I, ATG5, and Beclin-1 in HGFs. While HSP90AA1-siRNA transfected into Pg-LPS induced HGFs significantly reduced the HSP90AA1, HSP90α, HSP90β expression, decreased the inflammatory factors, ROS generation, cell apoptosis rate, and autophagy-related proteins and TLR2/4 protein levels. What's more, the addition of autophagy inhibitor 3-MA further promote the effect of HSP90AA1-siRNA on Pg-LPS treated HGFs.

CONCLUSIONS

This study showed that HSP90AA1 promoted the inflammatory response of Pg-LPS induced HGFs by regulating autophagy. The addition of 3-MA further confirmed that autophagy may mediate siHSP90AA1 to enhance the inflammatory response.

The Importance of CXCL1 in the Physiological State and in Noncancer Diseases of the Oral Cavity and Abdominal Organs

CXCL1 is a CXC chemokine, CXCR2 ligand and chemotactic factor for neutrophils. In this paper, we present a review of the role of the chemokine CXCL1 in physiology and in selected major non-cancer diseases of the oral cavity and abdominal organs (gingiva, salivary glands, stomach, liver, pancreas, intestines, and kidneys). We focus on the importance of CXCL1 on implantation and placentation as well as on human pluripotent stem cells. We also show the significance of CXCL1 in selected diseases of the abdominal organs, including the gastrointestinal tract and oral cavity (periodontal diseases, periodontitis, Sjögren syndrome, Helicobacter pylori infection, diabetes, liver cirrhosis, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), HBV and HCV infection, liver ischemia and reperfusion injury, inflammatory bowel disease (Crohn’s disease and ulcerative colitis), obesity and overweight, kidney transplantation and ischemic-reperfusion injury, endometriosis and adenomyosis).

The Effect of Porphyromonas gingivalis Lipopolysaccharide on the Pyroptosis of Gingival Fibroblasts

Periodontitis is a chronic inflammatory disease induced by Porphyromonas gingivalis (P. gingivalis) and other pathogens. P. gingivalis release various virulence factors including lipopolysaccharide (LPS). However, whether P. gingivalis-LPS inducing pyroptosis in human gingival fibroblasts (HGFs) remains unknown. In present study, P. gingivalis-LPS decreased the membrane integrity of HGFs, and pyroptosis-associated cytokines were upregulated at the mRNA level. In addition, pyroptosis proteins were highly expressed in gingival tissues of periodontitis. P. gingivalis-LPS induced gingivitis in the rat model, and the expression level of pyroptosis-associated proteins increased. Together, P. gingivalis-LPS can activate the pyroptosis reaction, which may be a pro-pyroptosis status in a relative low concentration.

Antioxidant Ascorbic Acid Modulates NLRP3 Inflammasome in LPS-G Treated Oral Stem Cells through NFκB/Caspase-1/IL-1β Pathway

Human gingival mesenchymal stem cells (hGMSCs) and endothelial committed hGMSCs (e-hGMSCs) have considerable potential to serve as an in vitro model to replicate the inflammation sustained by Porphyromonas gingivalis in periodontal and cardiovascular diseases. The present study aimed to investigate the effect of ascorbic acid (AA) on the inflammatory reverting action of lipopolysaccharide (LPS-G) on the cell metabolic activity, inflammation pathway and reactive oxygen species (ROS) generation in hGMSCs and e-hGMSCs. Cells were treated with LPS-G (5 μg mL⁻¹) or AA (50 μg mL⁻¹) and analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay, immunofluorescence and Western blot methods. The rate of cell metabolic activity was decreased significantly in LPS-G-treated groups, while groups co-treated with LPS-G and AA showed a logarithmic cell metabolic activity rate similar to untreated cells. AA treatment attenuated the inflammatory effect of LPS-G by reducing the expression of TLR4/MyD88/NFκB/NLRP3/Caspase-1/IL-1β, as demonstrated by Western blot analysis and immunofluorescence acquisition. LPS-G-induced cells displayed an increase in ROS production, while AA co-treated cells showed a protective effect. In summary, our work suggests that AA attenuated LPS-G-mediated inflammation and ROS generation in hGMSCs and e-hGMSCs via suppressing the NFκB/Caspase-1/IL-1β pathway. These findings indicate that AA may be considered as a potential factor involved in the modulation of the inflammatory pathway triggered by LPS-G in an vitro cellular model.

Knockdown of TRIM52 alleviates LPS-induced inflammatory injury in human periodontal ligament cells through the TLR4/NF-κB pathway

Tripartite motif-containing (TRIM) 52 (TRIM52) is a vital regulator of inflammation. However, the function and mechanisms of TRIM52 in lipopolysaccharide (LPS)-induced inflammatory injury of human periodontal ligament cells (HPDLCs) in periodontitis remain undefined. In the present research, gene expression was determined using a quantitative polymerase chain reaction and Western blot. The effect of TRIM52 on LPS-induced inflammatory injury was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and enyzme-linked immunosorbent assay (ELISA). We found that TRIM52 expression was up-regulated in LPS-treated HPDLCs. Knockdown of TRIM52 alleviated LPS-induced proliferative inhibition and apoptosis promotion in HPDLCs, as evidenced by a decrease in cleaved caspase-3 expression and caspase-3 activity. Silencing TRIM52 suppressed LPS-induced inflammatory response of HPDLCs, as indicated by the decrease in interleukin (IL)-6, IL-8, tumor necrosis factor-α (TNF-α) levels, and increase in IL-10 levels. TRIM52 knockdown inhibited LPS-induced activation of TLR4/nuclear factor-κ B (NF-κB) signaling pathway. Taken together, knockdown of TRIM52 mitigated LPS-induced inflammatory injury via the TLR4/NF-κB signaling pathway, providing an effective therapeutic target for periodontitis.

Hypoxia and Porphyromonas gingivalis-lipopolysaccharide synergistically induce NLRP3 inflammasome activation in human gingival fibroblasts

OBJECTIVE

To investigate the effects of hypoxia and Porphyromonas gingivalis- lipopolysaccharide (P. gingivalis-LPS) on activation of the NACHT leucine-rich repeat protein 3 (NLRP3) inflammasome in human gingival fibroblasts (HGFs).

DESIGN

Periodontitis was optimally simulated using a hypoxic concentration of 1%. HGFs were stimulated using P. gingivalis-LPS (1.0 μg/ml) in normoxia and hypoxia for 3 h and 6 h, respectively. The expression levels of genes and proteins of hypoxia-inducible factor-1α (HIF-1α), interleukin-1β, gasdermin D (GSDMD) and the NLRP3 inflammasome, including NLRP3, apoptosis-associated speck-like protein containing CARD (ASC), caspase-1 and its activated forms, were measured using quantitative real-time polymerase chain reaction and western blot. ELISA was used to detect and determine levels of the inflammatory factor interleukin-1β in cell supernatants. Lactate dehydrogenase (LDH) release assay, caspase-1 activity assay and Hoechst 33342/Propidium Iodide (PI) staining were performed to further verify the presence of pyroptosis.

RESULTS

The NLRP3 inflammasome (i.e., NLRP3, ASC, caspase-1) was not affected by individual stimulation using P. gingivalis-LPS or hypoxia. However, the combination of both hypoxia and P. gingivalis-LPS stimulation significantly enhanced inflammasome activation and promoted the expression of interleukin-1β, gasdermin D and HIF-1α at gene and protein levels; PI positive cells and the release of LDH were also elevated.

CONCLUSION

Hypoxia and P. gingivalis-LPS synergistically induced NLRP3 inflammasome activation in HGFs, and subsequently high levels of interleukin-1β and GSDMD-mediated pyroptosis can cause an HGF inflammatory response, which plays an important role in the pathogenesis of periodontitis.

The phenotype of gingival fibroblasts and their potential use in advanced therapies

Advanced therapies in medicine use stem cells, gene editing, and tissues to treat a wide range of conditions. One of their goals is to stimulate endogenous repair of tissues and organs by manipulating stem cells and their niche, as well as to optimize the intrinsic characteristics and plasticity of differentiated cells in adult tissues. In this context, fibroblasts emerge as an alternative source to stem cells because they share phenotypic and regenerative characteristics. Specifically, fibroblasts of the oral mucosae have been shown to have improved regenerative capacity compared to other fibroblast populations. Additionally, their easy access by means of minimally invasive procedures without generating aesthetic problems, with easy and rapid in vitro expansion and with great capacity to respond to extrinsic factors, make oral fibroblasts an attractive and interesting resource for regenerative medicine. This review summarizes current concepts regarding the phenotypic and functional aspects of human Gingival Fibroblasts and their niche, differentiating them from other fibroblast populations of oral-lining mucosa and skin fibroblasts. Furthermore, some applications are presented in regenerative medicine, emphasizing on the biological potential of human Gingival Fibroblasts.

Cynaroside protects human periodontal ligament cells from lipopolysaccharide-induced damage and inflammation through suppression of NF-κB activation

OBJECTIVE

To investigate whether cynaroside protects human periodontal ligament (hPDL) cells from lipopolysaccharide (LPS)-induced damage and inflammation and to analyze the underlying mechanism.

METHODS

LPS was used to stimulate hPDL and RAW264.7 cells. MTT assay was used to detect cell viability, and protein expression levels were measured via western blot analysis. Nitrite oxide and prostaglandin E₂ were used to quantify the inflammatory response. Alizarin Red S staining was used to detect mineralized nodules.

RESULTS

Cynaroside inhibited the expression of iNOS, COX-2, TNF-α, and IL-6 in LPS-stimulated hPDL and RAW264.7 cells without cytotoxicity. Furthermore, cynaroside significantly suppressed LPS-induced protein expression of matrix metalloproteinase 3. Additionally, cynaroside prevented LPS-induced NF-κB p65 subunit translocation to the nucleus by inhibiting the phosphorylation and degradation of IκB-α. Moreover, cynaroside could restore the mineralization ability of hPDL cells reduced by LPS.

CONCLUSION

Cynaroside protected hPDL cells from LPS-induced damage and inflammation via inhibition of NF-κB activation. These results suggest that cynaroside may be a potential therapeutic agent for the alleviation of periodontitis.

Involvement of Cathepsins in Innate and Adaptive Immune Responses in Periodontitis

Periodontitis is an infectious disease whereby the chronic inflammatory process of the periodontium stimulated by bacterial products induces specific host cell responses. The activation of the host cell immune system upregulates the production of inflammatory mediators, comprising cytokines and proteolytic enzymes, which contribute to inflammation and bone destruction. It has been well known that periodontitis is related to systemic inflammation which links to numerous systemic diseases, including diabetes and arteriosclerosis. Furthermore, periodontitis has been reported in association with neurodegenerative diseases such as Alzheimer's disease (AD) in the brain. Regarding immune responses and inflammation, cathepsin B (CatB) plays pivotal role for the induction of IL-1β, cathepsin K- (CatK-) dependent active toll-like receptor 9 (TLR9) signaling, and cathepsin S (CatS) which involves in regulating both TLR signaling and maturation of the MHC class II complex. Notably, both the production and proteolytic activities of cathepsins are upregulated in chronic inflammatory diseases, including periodontitis. In the present review, we focus on the roles of cathepsins in the innate and adaptive immune responses within periodontitis. We believe that understanding the roles of cathepsins in the immune responses in periodontitis would help to elucidate the therapeutic strategies of periodontitis, thus benefit for reduction of systemic diseases as well as neurodegenerative diseases in the global aging society.

CXCL1, CCL2, and CCL5 modulation by microbial and biomechanical signals in periodontal cells and tissues-in vitro and in vivo studies

OBJECTIVES

This study was established to investigate whether the chemokines CXCL1, CCL2, and CCL5 are produced in periodontal cells and tissues and, if so, whether their levels are regulated by microbial and/or mechanical signals.

MATERIALS AND METHODS

The chemokine expression and protein levels in gingival biopsies from patients with and without periodontitis were analyzed by RT-PCR and immunohistochemistry. The chemokines were also analyzed in gingival biopsies from rats subjected to experimental periodontitis and/or orthodontic tooth movement. Additionally, chemokine levels were determined in periodontal fibroblasts exposed to the periodontopathogen Fusobacterium nucleatum and mechanical forces by RT-PCR and ELISA.

RESULTS

Higher CXCL1, CCL2, and CCL5 levels were found in human and rat gingiva from sites of periodontitis as compared with periodontally healthy sites. In the rat experimental periodontitis model, the bacteria-induced upregulation of these chemokines was significantly counteracted by orthodontic forces. In vitro, F. nucleatum caused a significant upregulation of all chemokines at 1 day. When the cells were subjected simultaneously to F. nucleatum and mechanical forces, the upregulation of chemokines was significantly inhibited. The transcriptional findings were paralleled at protein level.

CONCLUSIONS

This study provides original evidence in vitro and in vivo that the chemokines CXCL1, CCL2, and CCL5 are regulated by both microbial and mechanical signals in periodontal cells and tissues. Furthermore, our study revealed that biomechanical forces can counteract the stimulatory actions of F. nucleatum on these chemokines.

CLINICAL RELEVANCE

Mechanical loading might aggravate periodontal infection by compromising the recruitment of immunoinflammatory cells.

Inhibition of the receptor for advanced glycation inhibits lipopolysaccharide-mediated High mobility group protein B1 and Interleukin-6 synthesis in human gingival fibroblasts through the NF-κB signaling pathway

AIMS

We investigated the effect of a specific inhibitor of the receptor for advanced glycation (FPS-ZM1) against lipopolysaccharide (LPS)-induced increase in expressions of high mobility group protein B1 (HMGB1) and interleukin-6 (IL-6) in human gingival fibroblasts (HGFs). Furthermore, we explored the potential molecular mechanisms and assessed the involvement of the NF-κB pathway in mediating the changes in the expressions of HMGB1 and IL-6 expression in response to LPS and FPS-ZM1.

METHODS

HGFs were cultured with enzymatic digestion-tissue explants method. The proliferation of LPS-stimulated HGFs pretreated with FPS-ZM1 at 24, 48, and 72 h was determined by cell counting kit 8 assay. The expressions of HMGB1 and IL-6 were measured using quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Western blot analysis was used to assess the expressions of receptor for advanced glycation end products (RAGE) and NF-κB.

RESULTS

LPS enhanced the protein expression of RAGE in HGFs. At the same time, LPS stimulated mRNA and protein expressions of HMGB1 and IL-6 in HGFs. However, pretreatment with FPS-ZM1 attenuated these effects. Pretreatment with FPS-ZM1 (250, 500 nM) significantly inhibited the LPS-induced NF-κB activity.

CONCLUSION

FPS-ZM1 down-regulated the LPS-induced HMGB1 and IL-6 expression in HGFs through blocking NF-κB activation. FPS-ZM1 is a promising therapeutic agent for inflammatory diseases caused by oral bacteria.

NFE2L2/NRF2, OGG1, and cytokine responses of human gingival keratinocytes against oxidative insults of various origin

OBJECTIVE

Bacterial or tobacco-related insults induce oxidative stress in gingival keratinocytes. The aim of this study was to investigate anti-oxidative and cytokine responses of human gingival keratinocytes (HMK cells) against Porphyromonas gingivalis lipopolysaccharide (Pg LPS), nicotine, and 4-nitroquinoline N-oxide (4-NQO).

MATERIALS AND METHODS

HMK cells were incubated with Pg LPS (1 µl/ml), nicotine (1.54 mM), and 4-NQO (1 µM) for 24 h. Intracellular and extracellular levels of interleukin (IL)-1β, IL-1 receptor antagonist (IL-1Ra), IL-8, monocyte chemoattractant protein (MCP)-1, and vascular endothelial growth factor (VEGF) were measured with the Luminex® xMAP™ technique, and nuclear factor, erythroid 2 like 2 (NFE2L2/NRF2) and 8-oxoguanine DNA glycosylase (OGG1) with Western blots. Data were statistically analyzed by two-way ANOVA with Bonferroni correction.

RESULTS

All tested oxidative stress inducers increased intracellular OGG1 levels, whereas only nicotine and 4-NQO induced NFE2L2/NRF2 levels. Nicotine, 4-NQO, and their combinational applications with Pg LPS induced the secretions of IL-1β and IL-1Ra, while that of IL-8 was inhibited by the presence of Pg LPS. MCP-1 secretion was suppressed by nicotine, alone and together with Pg LPS, while 4-NQO activated its secretion. Treatment of HMK cells with Pg LPS, nicotine, 4-NQO, or their combinations did not affect VEGF levels.

CONCLUSION

Pg LPS, nicotine, and 4-NQO induce oxidative stress and regulate anti-oxidative response and cytokine expressions in human gingival keratinocytes differently. These results may indicate that bacterial and tobacco-related insults regulate distinct pathways.

Correlation between crestal alveolar bone loss with intracanal bacteria and apical lesion area in necrotic teeth

OBJECTIVE

This study aimed to analyze the correlation between crestal alveolar bone loss with the presence of some bacterial species in root canals and the apical lesion area of necrotic teeth.

DESIGN

Data from 20 patients with diagnosis of pulp necrosis and acute apical abscesses, without active periodontal diseases, were evaluated. Patients with history of antibiotic usage three months prior to the study, with exposed pulp cavity, and with probing depth >3 mm were not included. The root size, the distance between the bone crest to the tooth apex in the mesial and distal surfaces, and the apical lesion area were measured from standard periapical radiographies by a calibrated examiner. Root canal samples were collected using sterilized paper points. In multirooted teeth, the largest root canal was sampled. Culture, microbial isolation and identification by phenotypic methods were performed. Spearman correlation and exact Fischer test were calculated between higher/lower existing bone crests, according to the median and the presence of specific bacteria.

RESULTS

No statistically significant differences were found between occurrence of pathogenic bacteria, such as Porphyromonas gingivalis, Porphyromonas endodontalis, and Prevotella intermedia, and groups with higher/lower degree of bone loss (p > 0.05). A negative significant correlation was found between Parvimonas micra and periodontal bone loss (p = 0.02). Additionally, no statistically significant association was found between crestal bone loss and the apical lesion area.

CONCLUSIONS

It was concluded that, in patients without active periodontitis, the presence of pathogenic bacteria in the root canal was not correlated with periodontal bone loss.