PKC, ERK/p38 MAP kinases and NF-κB targeted signalling play a role in the expression and release of IL-1β and CXCL8 in Porphyromonas gingivalis-infected THP1 cells

Integrative analysis of gene and protein expression in atherosclerosis-related pathways modulated by periodontal pathogens. Systematic review

The mechanisms modulated by periodontal pathogens in atherosclerosis are not fully understood. Aim: to perform an integrative analysis of gene and protein expression modulated by periodontal pathogens in cells and animal models for atherosclerosis.

Methods

Cochrane, PRISMA and AMSTAR2 guidelines for systematic reviews were followed. Data search was conducted in Pub-med, LILACS and Science Direct databases. Gene and protein expression data were collected from the included papers to perform an overrepresentation analysis using the Reactome Pathway Analysis tool and the KEGG database.

Results

Thirty-two papers were included in the review, they analyzed the effect of Fusobacterium nucleatum, Porphyromonas gingivalis, Streptococcus anginosus, Streptococcus sanguinis, Tannerella forsythia, and Treponema denticola or/and their virulent factors on gene and protein expression in human cells and animal models of atherosclerosis. Some of the modulated pathways include the immune system, programmed cell death, cellular responses to external stimuli, transport of small molecules, and signal transduction (p < 0.05). Those pathways are known to be involved in different stages of atherosclerosis progression.

Conclusion

Based on the performed analysis, it is possible to state that periodontal pathogens have the potential to be a contributing factor for atherosclerosis even in absence of a high-fat diet or high shear stress.

Critical roles of PU.1/cathepsin S activation in regulating inflammatory responses of macrophages in periodontitis

OBJECTIVE

To determine the critical roles of PU.1/cathepsin S activation in regulating inflammatory responses of macrophages during periodontitis.

BACKGROUND

Cathepsin S (CatS) is a cysteine protease and exerts important roles in the immune response. Elevated CatS has been found in the gingival tissues of periodontitis patients and is involved in alveolar bone destruction. However, the underlying mechanism of CatS-driven IL-6 production in periodontitis remains unclear.

METHODS

Western blot was applied to measure mature cathepsin S(mCatS) and IL-6 expression in gingival tissues from periodontitis patients and RAW264.7 cells exposed to lipopolysaccharide from Porphyromonas gingivalis (P.g. LPS). Immunofluorescence was applied to confirm the localization of PU.1, and CatS in the gingival tissues of periodontitis patients. ELISA was performed to determine IL-6 production by the P.g. LPS-exposed RAW264.7 cells. Knockdown by shRNA was used to determine the effects of PU.1 on p38/ nuclear factor (NF)-κB activation, mCatS expression and IL-6 production in RAW264.7 cells.

RESULTS

The expressions mCatS and IL-6 were significantly upregulated in gingival macrophages. In cultured RAW264.7 cells, increased mCatS and IL-6 protein paralleled the activation of p38 and NF-κB after exposure to P.g. LPS. CatS knockdown by shRNA significantly decreased P.g. LPS-induced IL-6 expression and p38/NF-κB activation. PU.1 was significantly increased in P.g. LPS-exposed RAW264.7 cells, and PU.1 knockdown dramatically abolished the P.g. LPS-induced upregulation of mCatS and IL-6 and the activation of p38 and NF-κB. Furthermore, PU.1 and CatS colocalized in macrophages within the gingival tissues of periodontitis patients.

CONCLUSION

PU.1-dependent CatS drives IL-6 production in macrophages by activating p38 and NF-κB in periodontitis.

Porphyromonas gingivalis Gingipains Induce Cyclooxygenase-2 Expression and Prostaglandin E2 Production via ERK1/2-Activated AP-1 (c-Jun/c-Fos) and IKK/NF-κB p65 Cascades

Porphyromonas gingivalis is commonly known as one of the major pathogens contributing to periodontitis, and its persistent infection may increase the risk for the disease. The proinflammatory mediators, including IL-6, TNF-α, and cyclooxygenase-2 (COX-2)/PGE₂, are closely associated with progression of periodontitis. In this study, we focused on the cysteine protease "gingipains," lysine-specific gingipain, arginine-specific gingipain (Rgp) A, and RgpB, produced by P. gingivalis, and used the wild-type strain and several gene-deletion mutants (rgpA, rgpB, kgp, and fimA) to elucidate the involvement of gingipains in COX-2 expression and PGE₂ production. We infected human monocytes, which are THP-1 cells and primary monocytes, with these bacterial strains and found that gingipains were involved in induction of COX-2 expression and PGE₂ production. We have shown that the protease activity of gingipains was crucial for these events by using gingipain inhibitors. Furthermore, activation of ERK1/2 and IκB kinase was required for gingipain-induced COX-2 expression/PGE₂ production, and these kinases activated two transcription factors, c-Jun/c-Fos (AP-1) and NF-κB p65, respectively. In particular, these data suggest that gingipain-induced c-Fos expression via ERK is essential for AP-1 formation with c-Jun, and activation of AP-1 and NF-κB p65 plays a central role in COX-2 expression/PGE₂ production. Thus, we show the (to our knowledge) novel finding that gingipains with the protease activity from P. gingivalis induce COX-2 expression and PGE₂ production via activation of MEK/ERK/AP-1 and IκB kinase/NF-κB p65 in human monocytes. Hence it is likely that gingipains closely contribute to the inflammation of periodontal tissues.

Inherently and Conditionally Essential Protein Catabolism Genes of Porphyromonas gingivalis

Proteases are critical virulence determinants of Porphyromonas gingivalis, an emerging Alzheimer's disease, cancer, and arthritis pathogen and established agent of periodontitis. Transposon sequencing has been employed to define the core essential genome of this bacterium and genes conditionally essential in multiple environments - abscess formation; epithelial colonization; and cigarette smoke toxin exposure; as well as to elucidate genes required for iron acquisition and a functional type 9 secretion system. Validated and predicted protein catabolism genes identified include a combination of established virulence factors and a larger set of seemingly more mundane proteolytic genes. The functions and relevance of genes that share essentiality in multiple disease-relevant conditions are examined. These common stress-related genes may represent particularly attractive therapeutic targets for the control of P. gingivalis infections.

GLP-1 inhibits PKCβ2 phosphorylation to improve the osteogenic differentiation potential of hPDLSCs in the AGE microenvironment

BACKGROUND AND OBJECTIVE

Advanced glycation end products (AGEs) have been hypothesized as the etiologic factors of diabetic periodontitis. The discovery of incretins (including GLP-1 and GIP) provides a novel therapy for the treatment of diabetes. Recent reports have shown that glucagon-like peptide-1 (GLP-1) is an important modulator of bone growth and remodeling. The aim of this study was to clarify the mechanism of how GLP-1 weakens/inhibits the effect of AGEs in hPDLSCs (human periodontal ligament stem cells).

MATERIALS AND METHODS

The hPDLSCs were cultured under simulated conditions of osteogenic culture, AGEs, AGEs + GLP-1, AGEs + GLP-1 + PMA and AGEs + GLP-1 + LY333531. The phenomenon and related mechanism of cell osteogenesis under different microenvironments were evaluated by Alizarin red staining, ALP staining and quantitative activity measurement, RT-qPCR, western blotting and immunofluorescence staining.

RESULTS

RT-qPCR showed that AGEs negatively regulated the expression of osteogenic differentiation markers (ALP, BSP, OPN, and Runx2); in contrast, GLP-1 increased the expression of these markers. Furthermore, the expression of RAGE and pPKCβ (PKC phosphorylation) in the AGE group was upregulated, while the expression of RAGE and pPKCβ was decreased in the GLP-1 group compared with the AGE group.

CONCLUSIONS

AGEs impaired the osteogenic potential of hPDLSCs via PKCβ2. Our phenomenon showed that GLP-1 could reverse the function of AGEs on osteogenic potential. In addition, the mechanism of GLP-1 weakens/inhibits the effect of AGEs in hPDLSCs, possibly by inhibiting PKCβ2 phosphorylation.

Porphyromonas gingivalis-Induced MIF Regulates Intercellular Adhesion Molecule-1 Expression in EA.hy926 Cells and Monocyte-Endothelial Cell Adhesion Through the Receptors CD74 and CXCR4

Porphyromonas gingivalis (P. gingivalis) is an important pathogen that contributes to periodontal disease and causes infections that promote the progression of atherosclerosis. Our previous studies showed that macrophage migration inhibitory factor (MIF) facilitates monocyte adhesion to endothelial cells by regulating the expression of intercellular adhesion molecule-1 (ICAM-1) in P. gingivalis-infected endothelial cells. However, the detailed pathological role of MIF has yet to be elucidated in this context. To explore the functional receptor(s) of MIF that underlie its participation in the pathogenesis of atherosclerosis, we investigated the expression of the chemokine receptors CD74 and CXCR4 in endothelial cells, both of which were shown to be involved in the adhesion of monocytes to endothelial cells pretreated with P. gingivalis. Furthermore, the formation of a MIF, CD74, and CXCR4 ligand-receptor complex was revealed by our immunofluorescence staining and coimmunoprecipitation results. By interacting with the CD74/CXCR4 receptor complex, MIF may act as a crucial regulator of monocyte-endothelial cell adhesion and promote the atherosclerotic plaque formation induced by P. gingivalis.

PKC Mediates LPS-Induced IL-1β Expression and Participates in the Pro-inflammatory Effect of A2AR Under High Glutamate Concentrations in Mouse Microglia

Pathogens such as bacterial lipopolysaccharide (LPS) play an important role in promoting the production of the inflammatory cytokines interleukin-1 beta (IL-1β) and tumour necrosis factor-α (TNF-α) in response to infection or damage in microglia. However, whether different signalling pathways regulate these two inflammatory factors remains unclear. The protein kinase C (PKC) family is involved in the regulation of inflammation, and our previous research showed that the activation of the PKC pathway played a key role in the LPS-induced transformation of the adenosine A_2A receptor (A_2AR) from anti-inflammatory activity to pro-inflammatory activity under high glutamate concentrations. Therefore, in the current study, we investigated the role of PKC in the LPS-induced production of these inflammatory cytokines in mouse primary microglia. GF109203X, a specific PKC inhibitor, inhibited the LPS-induced expression of IL-1β messenger ribonucleic acid and intracellular protein in a dose-dependent manner. Moreover, 5 µM GF109203X prevented LPS-induced IL-1β expression but did not significantly affect LPS-induced TNF-α expression. PKC promoted IL-1β expression by regulating the activity of NF-κB but did not significantly impact the activity of ERK1/2. A_2AR activation by CGS21680, an A_2AR agonist, facilitated LPS-induced IL-1β expression through the PKC pathway at high glutamate concentrations but did not significantly affect LPS-induced TNF-α expression. Taken together, these results suggest a new direction for specific intervention with LPS-induced inflammatory factors in response to specific signalling pathways and provide a mechanism for A_2AR targeting, especially after brain injury, to influence inflammation by interfering with A_2AR.

Evaluation of the effect of oleuropein on alveolar bone loss, inflammation, and apoptosis in experimental periodontitis

THE OBJECTIVE

The present study aimed to evaluate the effects of oleuropein on ligature-induced alveolar bone loss. In this respect, osteoblastic activity, osteoclastic activity, inflammatory markers, and apoptosis were evaluated.

BACKGROUND

Oleuropein is a flavonoid, which has potent anti-inflammatory and bone-protective effects.

METHODS

Thirty-two Wistar rats were divided into four experimental groups as following: control (C, n = 8) group; periodontitis (P, n = 8) group; periodontitis and low-dose oleuropein group (12 mg/kg/day oleuropein, LDO group, n = 8); and periodontitis and high-dose oleuropein group (24 mg/kg/day oleuropein, HDO group, n = 8). Periodontitis was induced via ligatures. Study period was 14 days, and animals were sacrificed at end of this period. Mandibles were examined via a stereomicroscope and underwent histological procedures. Osteoblast, tartrate-resistant acid phosphatase (TRAP)-positive osteoclast, and inflammatory cell counts were determined in hematoxylin-eosin stained sections. Inducible nitric oxide synthase (iNOS), bone morphogenetic protein-4, the cluster of differentiation (CD)-68, cysteine-aspartic proteases-3 (Caspase 3), and B-cell lymphoma-2 (Bcl-2) expressions were evaluated via immunohistochemistry.

RESULTS

Periodontitis group had highest alveolar bone loss, and these levels significantly decreased in LDO and HDO groups. Both 12 and 24 mg/kg oleuropein groups significantly increased osteoblast cell counts and decreased TRAP-positive osteoclast and inflammatory cell counts. BMP-4 and bcl-2 expressions were elevated in oleuropein groups while caspase-3 expressions decreased. iNOS and CD68 were higher in periodontitis group compared to control group, but there was no significant difference between other groups.

CONCLUSION

Oleuropein successfully decreased alveolar bone loss as a result of decreased osteoclastic activity, inflammation, and apoptosis and increased osteoblastic activity.

Upregulated expression of HOXB7 in intrahepatic cholangiocarcinoma is associated with tumor cell metastasis and poor prognosis

Homeobox B7 (HOXB7) protein is reported to be aberrantly expressed in a variety of cancers and to play an important role in multiple cellular processes. However, the specific mechanism by which HOXB7 promotes the malignant progression of intrahepatic cholangiocarcinoma (ICC) remains unclear. Therefore, we used quantitative real-time polymerase chain reaction (PCR) to detect the expression level of HOXB7 in 38 paired ICC tissue samples. Additionally, to assess correlation between HOXB7 and ICC prognosis, we performed immunohistochemistry (IHC) using 122 ICC tissues to detect HOXB7 expression. Cell Counting Kit-8 (CCK-8) and colony formation assays were employed to assess ICC cell proliferation, and Transwell assays were performed to estimate the invasion and migration abilities of ICC cells. The capillary tube formation assay was applied to explore the angiogenic effects of HOXB7. A xenograft tumor model was established in nude mice to assess the role of HOXB7 in tumor growth and lung metastasis. The results showed higher expression of HOXB7 in ICC tissues than in noncancerous tissues, and this increased expression was significantly associated with a poor prognosis. In addition, HOXB7 overexpression enhanced capillary tube formation, invasion and migration of ICC cells in vitro, whereas HOXB7 knockdown produced the opposite results in vitro. Moreover, the role of HOXB7 in promoting tumor growth and metastasis was verified in vivo. Further investigation revealed that the expression levels of MMP2, MMP9, VEGFa, and IL8 were elevated by HOXB7 and that the ERK pathway was activated. Our results demonstrate the prognostic value of HOXB7 and its role in metastasis and angiogenesis in ICC. HOXB7 upregulated MMP2, MMP9, VEGFa, and IL8 expression via the ERK pathway to accelerate the malignant progression of ICC.

Staphylococcus epidermidis from prosthetic joint infections induces lower IL-1β release from human neutrophils than isolates from normal flora

The aim of this study was to test the hypothesis that Staphylococcus epidermidis isolated from prosthetic joint infections (PJIs) differs from S. epidermidis isolated from normal flora in terms of its capacity to induce activation of caspase-1 and release of IL-1β in human neutrophils. The amount of active caspase-1 was determined over 6 h by detecting Ac-YVAD-AMC fluorescence in human neutrophils incubated with S. epidermidis isolates from PJIs (ST2) or normal flora. The amount of IL-1β was detected by ELISA in neutrophil supernatants after 6 h of incubation. Mean IL-1β release was lower after incubation with S. epidermidis from PJIs compared to isolates from normal flora, but no statistically significant difference was found in active caspase-1. Substantial inter-individual differences in both active caspase-1 and IL-1β were noted. These results suggest that evasion of innate immune response, measured as reduced capacity to induce release of IL-1β from human neutrophils, might be involved in the predominance of ST2 in S. epidermidis PJIs, but that other microbe-related factors are probably also important.

Differential modulation by vanadium pentoxide of the secretion of CXCL8 and CXCL11 chemokines in thyroid cells

Recently it has been hypothesized that vanadium serves a carcinogenic role in the thyroid. However, to date, no in vivo or in vitro studies have evaluated thyroid disruption in humans and/or animals following exposure to vanadium. The present study evaluated the effect of vanadium pentoxide (V2O5) on cell viability and proliferation, and chemokine (C‑X‑C motif) ligand (CXCL)8 and CXCL11 secretion in normal thyrocytes. The results demonstrated that V2O5 had no effect on thyroid follicular cell viability and proliferation. However, V2O5 was able to induce the secretion of CXCL8 and CXCL11 chemokines from thyrocytes. Notably, V2O5 synergistically increased the effect of the interferon (IFN)‑γ on CXCL11 secretion. In addition, V2O5 synergistically increased the effect of tumor necrosis factor‑α on CXCL8 secretion, and abolished the inhibitory effect of IFN‑γ. Overall this induction of CXCL8 and CXCL11 secretion may lead to the induction and perpetuation of an inflammatory reaction in the thyroid. Further studies are now required to evaluate thyroid function and nodule development in subjects who are occupationally exposed, or living in polluted areas.