Rosiglitazone impedes Porphyromonas gingivalis-accelerated atherosclerosis by downregulating the TLR/NF-κB signaling pathway in atherosclerotic mice

Porphyromonas gingivalis regulates atherosclerosis through an immune pathway

Atherosclerosis (AS) is a chronic inflammatory disease, involving a pathological process of endothelial dysfunction, lipid deposition, plaque rupture, and arterial occlusion, and is one of the leading causes of death in the world population. The progression of AS is closely associated with several inflammatory diseases, among which periodontitis has been shown to increase the risk of AS. Porphyromonas gingivalis (P. gingivalis), presenting in large numbers in subgingival plaque biofilms, is the “dominant flora” in periodontitis, and its multiple virulence factors are important in stimulating host immunity. Therefore, it is significant to elucidate the potential mechanism and association between P. gingivalis and AS to prevent and treat AS. By summarizing the existing studies, we found that P. gingivalis promotes the progression of AS through multiple immune pathways. P. gingivalis can escape host immune clearance and, in various forms, circulate with blood and lymph and colonize arterial vessel walls, directly inducing local inflammation in blood vessels. It also induces the production of systemic inflammatory mediators and autoimmune antibodies, disrupts the serum lipid profile, and thus promotes the progression of AS. In this paper, we summarize the recent evidence (including clinical studies and animal studies) on the correlation between P. gingivalis and AS, and describe the specific immune mechanisms by which P. gingivalis promotes AS progression from three aspects (immune escape, blood circulation, and lymphatic circulation), providing new insights into the prevention and treatment of AS by suppressing periodontal pathogenic bacteria.

Fusobacterium nucleatum Accelerates Atherosclerosis via Macrophage-Driven Aberrant Proinflammatory Response and Lipid Metabolism

Periodontitis, an oral chronic inflammatory disease, is reported to show an association with atherosclerotic vascular disease. Fusobacterium nucleatum is an oral commensal bacterium that is abundantly implicated in various forms of periodontal diseases; however, its role in the pathogenesis of atherosclerosis is unclear. This study aimed to elucidate the underlying pathogenic mechanisms of atherosclerosis induced by F. nucleatum to provide new insight on the prevention and treatment of atherosclerosis. We used an animal model, that is, ApoE^–/– mice were infected with F. nucleatum by oral gavage, and in vitro co-culture models to assess the pathogenicity of F. nucleatum. The results indicate that F. nucleatum ATCC 25586 invaded aortic tissues and substantially increased the progression of atherosclerotic lesions. In addition, F. nucleatum changed plaque composition into a less-stable phenotype, characterized with increased subcutaneous macrophage infiltration, M1 polarization, lipid deposition, cell apoptosis, and reduced extracellular matrix and collagen content. The serum levels of pro-atherosclerotic factors, such as interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, monocyte chemoattractant protein-1 (MCP-1), c-reactive protein, and oxidized low-density lipoprotein (ox-LDL) and microRNAs (miR-146a, miR-155, and miR-23b) were considerably increased after F. nucleatum stimulation, whereas HDL-c level was reduced. F. nucleatum induced in vitro macrophage apoptosis in a time- and dose-dependent manner. F. nucleatum facilitated ox-LDL–induced cholesterol phagocytosis and accumulation by regulating the expression of lipid metabolism-related genes (AR-A1, ACAT1, ABCA1, and ABCG1). F. nucleatum further worsened the atherosclerotic plaque microenvironment by considerably increasing the levels of IL-6; IL-1β; TNF-α; MCP-1; and MMP-2, 8, and 9 and by suppressing fibronectin (FN) 1 levels during foam cell formation. This study shows that F. nucleatum ATCC 25586 is implicated in atherosclerosis by causing aberrant activation and lipid metabolism in macrophage.

Periodontopathic Microbiota and Atherosclerosis: Roles of TLR-Mediated Inflammation Response

Atherosclerosis is a chronic inflammatory disease with a high prevalence worldwide, contributing to a series of adverse cardiovascular and cerebrovascular diseases. Periodontal disease induced by pathogenic periodontal microbiota has been well established as an independent factor of atherosclerosis. Periodontal microorganisms have been detected in atherosclerotic plaques. The high-risk microbiota dwelling in the subgingival pocket can stimulate local and systematic host immune responses and inflammatory cascade reactions through various signaling pathways, resulting in the development and progression of atherosclerosis. One often-discussed pathway is the Toll-like receptor-nuclear factor-κB (TLR-NF-κB) signaling pathway that plays a central role in the transduction of inflammatory mediators and the release of proinflammatory cytokines. This narrative review is aimed at summarizing and updating the latest literature on the association between periodontopathic microbiota and atherosclerosis and providing possible therapeutic ideas for clinicians regarding atherosclerosis prevention and treatment.

Effects of chronic apical periodontitis on the inflammatory response of the aorta in hyperlipemic rats

OBJECTIVES

To study the effects of chronic apical periodontitis (CAP) on the inflammatory response and initial lesion of aorta in hyperlipemic rats.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats aged 14 weeks were randomly divided into 4 experimental groups (n = 8), namely, normal diet (ND), high-fat diet (HFD), CAP, and HFD + CAP. The rats were raised under controlled conditions and fed with diet specified for each group. All subjects were euthanatized after 14 weeks for histopathological analysis. Serum cytokines were analyzed to assess changes in gene and protein expression of aorta via enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Results were analyzed by one-way ANOVA.

RESULTS

Low-density lipoprotein cholesterol levels in rats in HFD + CAP group were significantly higher than those in other groups. By comparison, low-density lipoprotein cholesterol levels in rats in both the HFD and HFD + CAP groups were significantly lower than those in the other groups. No significant difference among all groups was observed in terms of CRP level. However, levels of IL-2, IL-6, and IL-10 increased in the experimental CAP rats compared with the control rats. mRNA expression levels of MCP-1, TLR-4, and NF-κB p65 were markedly elevated in rats in the HFD group compared with those in rats in the ND group. TLR-4 mRNA expression was significantly higher in rats in the HFD + CAP group than that in rats in the HFD group.

CONCLUSIONS

CAP mediated the high expression of cytokines and induced the initial inflammatory response in the aorta. Apical periodontitis may affect the level of inflammatory cytokines (IL-2, IL-6, and IL-10) depending on the immune response.

CLINICAL RELEVANCE

CAP may trigger a systemic inflammatory response and affect the aorta of patients.

[Effect of Porphyromonas gingivalis infection on atherosclerosis in apolipoprotein-E knockout mice]

OBJECTIVE

Studies have indicated that periodontal pathogen Porphyromonas gingivalis (P. gingivalis) infection may contributed to accelerate the development of atherosclerosis. The aim of this study was to investigate the effect of inflammation, oxidative stress and the mechanism on atherosclerosis in apolipoprotein-E knockout (ApoE-/-) mice with P. gingivalis infection.

METHODS

Eight-week-old male ApoE-/- mice (C57BL/6) were maintained under specific pathogen-free conditions and fed regular chow and sterile water after 1 weeks of housing. The animals were randomly divided into two groups: (a) ApoE-/- + PBS (n=8); (b) ApoE-/- + P.gingivalis strain FDC381 (n=8). Both of the groups received intravenous injections 3 times per week for 4 weeks since 8 weeks of age. The sham control group received injections with phosphate buffered saline only, while the P. gingivalis-challenged group with P.gingivalis strain FDC381at the same time. After 4 weeks, oxidative stress mediators and inflammation cytokines were analyzed by oil red O in heart, Enzyme linked immunosorbent assay (ELISA) in serum, quantitative real-time PCR and Western blot in aorta.

RESULTS

In our study, we found accelerated development of atherosclerosis and plaque formation in aorta with oil red O staining, increased oxidative stress markers [8-hydroxy-2-deoxyguanosine (8-OHdG), NADPH oxidase (NOX)-2 and NOX-4], as well as increased inflammation cytokines [interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α)] in the serum and aorta of the P. gingivalis-infected ApoE-/- mice. Compared with the control group, there was a significant increase protein level of nuclear factor-kappa B (NF-κB) in aorta after P. gingivalis infection.

CONCLUSIONS

Our results suggest that chronic intravenous infection of P. gingivalis in ApoE-/- mice could accelerate the development of atherosclerosis by disturbing the lipid profile and inducing oxidative stress and inflammation. The NF-κB signaling pathway might play a potential role in the P. gingivalis-accelerated atherogenesis.

Protective effect of rivaroxaban on arteriosclerosis obliterans in rats through modulation of the toll-like receptor 4/NF-κB signaling pathway

The aim of the present study was to explore the pharmacological role of rivaroxaban in rats with arteriosclerosis obliterans (ASO) and the potential mechanism of its action. A total of 60 adult male Sprague Dawley (weighing 210–250 g) were randomly assigned into either the sham group, model group or Riv group. Rats in the sham group were fed a normal diet, whereas those in model group and Riv group were fed a high-fat diet for 8 weeks. After establishment of the ASO model, rats in the Riv group were intragastrically administered 10 mg/kg rivaroxaban, whereas those in the sham group and the model group were administrated with the same volume of 0.9% saline for 4 weeks. At the end of animal procedures, a blood sample and the femoral artery of the rats were harvested. The results of the present study revealed that rats in the model group presented with an irregularly narrowed femoral artery lumen, disordered endothelial cells, internal elastic plates and smooth muscle cells. By comparison, the arterial wall structure and stenosis of the femoral artery of rats in Riv group recovered and all the pathological changes were alleviated after rivaroxaban treatment. Levels of total cholesterol, triglycerides and low-density lipoproteins decreased, whereas the level of high-density lipoproteins increased in the Riv group compared with the model group. Rivaroxaban treatment significantly reduced serum levels of interleukin-1, tumor necrosis factor-α and monocyte chemoattractant protein-1 (MCP-1), and increased the serum level of transforming growth factor-β (TGF-β). Rats in the Riv group had reduced expression of toll-like receptor 4 (TLR4), NF-κB and MCP-1, and increased expression of TGF-β in femoral artery tissues compared with the model group. Therefore rivaroxaban may have exerted its anti-atherosclerotic effects by regulating the expression of genes in the TLR4/NF-κB signaling pathway and the activation of the downstream molecules.

Tanshinone IIA Attenuates Atherosclerosis in Apolipoprotein E Knockout Mice Infected with Porphyromonas gingivalis

Tanshinone IIA (TSA), a pharmacologically active component isolated from Danshen, may prevent cardiovascular diseases due to its anti-inflammatory, anti-oxidative, and anti-adipogenic effects. Porphyromonas gingivalis, a major periodontal pathogen, may contribute to the progression of atherosclerosis. Here, we studied the effects of TSA on atherosclerosis in ApoE^-/- mice with P. gingivalis infection. Eight-week-old ApoE^-/- mice were randomized to (a) phosphate-buffered saline (PBS), (b) P. gingivalis, and (c) P. gingivalis + TSA (60 mg kg^-1 day^-1). The mice were injected with (a) PBS, or (b) and (c) P. gingivalis 3 times per week for a total of 10 times. After 8 weeks, atherosclerotic risk factors in serum and in heart, aorta, and liver tissues were analyzed in all mice using Oil Red O, atherosclerosis cytokine antibody arrays, enzyme-linked immunosorbent assay (ELISA), real-time PCR, and microRNA array. CD40, G-CSF, IFN-γ, interleukin (IL)-1β, IL-6, MCP-1, MIP-3α, tumor necrosis factor-α (TNF-α), and VEGF were attenuated by TSA in atherosclerosis cytokine antibody arrays. TSA-treated mice showed a significant reduction of C-reactive protein (CRP), ox-LDL, IL-1β, IL-6, IL-12, and TNF-α in ELISA data. Real-time PCR analyses showed that TSA decreased the expression of CCL-2, CD40, IL-1β, IL-6, TNF-α, and MMP-2 in heart and aorta tissues. Moreover, hepatic CRP was downregulated by TSA, although FASN and HMG-CoA were not. The relative expressions of miR-146b and miR-155 were elevated by P. gingivalis infection and were downregulated by TSA treatment. These results suggest that TSA was a potential therapeutic agent that may have the ability to prevent P. gingivalis-induced atherosclerosis associated with anti-inflammatory and anti-oxidative effects.

Therapeutic effects of fibroblast growth factor‑21 against atherosclerosis via the NF‑κB pathway

Fibroblast growth factor‑21 (FGF‑21) is a pleiotropic protein predominantly secreted in the liver, adipose tissue and pancreas. It has been reported that the metabolic hormone effects of FGF‑21 on energy metabolism are essential for human vascular endothelial cells. The aim of the present study was to investigate the therapeutic effects and the underlying primary mechanism of FGF‑21 on atherosclerosis in a rat model induced by vitamin D3 and a high fat diet. The rats with atherosclerosis were randomly divided into vehicle (PBS; negative control), FGF‑21 (6 mg/kg/d) and atorvastatin (6 mg/kg/d; positive control) groups (n=40 in each group). The rats with atherosclerosis received continuous drug or PBS administration via intravenous injection for a treatment period of 30 days, following which all animals were sacrificed. The expression levels of FGF‑21 were determined prior to and following treatment with the drug or PBS. Alterations in ultrastructure and histopathology in vascular endothelial cells were examined, and the expression of nuclear transcription factor kappa B (NF‑κB) and levels of blood lipids in the thoracic aorta tissues were also determined. The results showed that typical atheromatous plaques formed, and the mRNA and protein expression levels of FGF‑21 were lower in the vascular endothelial cells of the rats with atherosclerosis, compared with the normal rats. FGF‑21 significantly reduced blood lipids and glucose in the rats with atherosclerosis, compared with those in the PBS and atorvastatin groups (P<0.01). The expression levels of Rho kinase and NF‑κB were significantly lower in the FGF‑21 group, compared with the normal control group (P<0.01). Statistically significant differences were found in atheromatous plaques and inflammatory factors in the FGF‑21 group, compared with the PBS and atorvastatin groups (P<0.01). In conclusion, FGF‑21 significantly downregulated the levels of blood lipids, Rho kinase and NF‑κB, which contributed to atherosclerosis therapy in the model rats and indicated the potential mechanisms against atherosclerosis in the model rats.

Silencing Triggering Receptors Expressed on Myeloid Cells-1 Impaired the Inflammatory Response to Oxidized Low-Density Lipoprotein in Macrophages

Atherosclerosis is a chronic progressive inflammatory disease characterized by the accumulation of lipid contents in arterial walls. Previous studies suggest participation of Toll-like receptors (TLRs) in lipid deposition and inflammatory response in vascular wall. The triggering receptor expressed on myeloid cells 1 (TREM-1) is a cell surface receptor of the immunoglobulin superfamily, which amplifies signal transduction of TLR pathway and enhances immune response to microbial infections. The aim of the present study was to investigate the effect of the oxidized low-density lipoprotein (oxLDL) on the expression of the TREM-1, as well as its engagement in proinflammatory cytokine production and foam cell formation in RAW264.7 mice macrophages. oxLDL enhanced TREM-1 and TLR-4, but not TLR-2 gene expression in macrophages; furthermore, silencing TREM-1 expression by short hairpin interfering RNA inhibited lipid phagocytosis and proinflammatory tumor necrosis factor-α (TNF-α) as well as interleukin-6 (IL-6) production in macrophages; moreover, application of synthetic antagonist, LP-17 polypeptide, reduced IL-6 production upon oxLDL stimulation in vitro and in vivo. In conclusion, in macrophages, oxLDL enhanced expression of TREM-1, which amplifies the innate immune response of TLR pathway; activation of TREM-1 contributes to atherogenesis process by enhancing proinflammatory cytokine production and foam cell formation.

The molecular mechanisms of action of PPAR-γ agonists in the treatment of corneal alkali burns (Review)

Corneal alkali burns (CAB) are characterized by injury-induced inflammation, fibrosis and neovascularization (NV), and may lead to blindness. This review evaluates the current knowledge of the molecular mechanisms responsible for CAB. The processes of cytokine production, chemotaxis, inflammatory responses, immune response, cell signal transduction, matrix metalloproteinase production and vascular factors in CAB are discussed. Previous evidence indicates that peroxisome proliferator-activated receptor γ (PPAR-γ) agonists suppress immune responses, inflammation, corneal fibrosis and NV. This review also discusses the role of PPAR-γ as an anti-inflammatory, anti-fibrotic and anti-angiogenic agent in the treatment of CAB, as well as the potential role of PPAR-γ in the pathological process of CAB. There have been numerous studies evaluating the clinical profiles of CAB, and the aim of this systematic review was to summarize the evidence regarding the treatment of CAB with PPAR-γ agonists.

Nonsurgical periodontal treatment reduced aortic inflammation in ApoE(-/-) mice with periodontitis

Background

Although the correlation between periodontal infection and atherosclerotic lesions has been well recognized, whether and how the nonsurgical periodontal treatment (NSPT) can improve the vascular inflammation has not been investigated clearly.

Methods

Thirty-two apolipoprotein E^−/− (apoE^−/−) mice were randomly divided into four groups: (1) Con group: no treatment, blank control group; (2) Lig group: ligature-induced-periodontitis group; (3) Lig-N group: ligatures were removed on the 7th day; (4) Lig-SRP group: ligatures were removed on the 7th day, and scaling and root planing (SRP) were performed on the 9th day. All the animals were euthanized on the 30th day. Alveolar bone loss (ABL) was assessed under microcomputed tomography. Systemic inflammatory status and lipid contents in the plasma were detected. Expression of several surrogate markers for vascular inflammation was evaluated by immunohistology and quantitative real time PCR.

Results

NSPT reduced ABL, improved lipid profile, and inhibited systemic inflammation with reduced plasma interleukin-6 (IL-6) level in apoE^−/− mice; in addition, reduced inflammation in arterial wall was observed in NSPT treated mice, showing less vascular cell adhesion molecule-1 expression and less macrophage adhesion; furthermore, NSPT improved elastic fiber fragmentation disorder in the aortic wall, thus preserved elasticity of aortic artery.

Conclusion

Ligature-induced periodontitis can lead to inflammatory response in the vascular wall and NSPT has beneficial effect on the early stage of atherosclerosis process in the articular wall by reducing systemic inflammation and improving lipid profile.