Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Infection with bacteria such as Chlamydia pneumonia, Helicobacter pylori or Porphyromonas gingivalis may be triggering the secretion of inflammatory cytokines that leads to atherogenesis. The mechanisms by which the innate immune recognition of these pathogens could lead to atherosclerosis remain unclear. In this study, using human vascular endothelial cells or HEK-293 cells engineered to express pattern-recognition receptors (PRRs), we set out to determine Toll-like receptors (TLRs) and functionally associated PRRs involved in the innate recognition of and response to lipopolysaccharide (LPS) from H. pylori or P. gingivalis. Using siRNA interference or recombinant expression of cooperating PRRs, we show that H. pylori and P. gingivalis LPS-induced cell activation is mediated through TLR2. Human vascular endothelial cell activation was found to be lipid raft-dependent and to require the formation of heterotypic receptor complexes comprising of TLR2, TLR1, CD36 and CD11b/CD18. In addition, we report that LPS from these bacterial strains are able to antagonize TLR4. This antagonistic activity of H. pylori or P. gingivalis LPS, as well as their TLR2 activation capability may be associated with their ability to contribute to atherosclerosis.
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PMID:Lipopolysaccharides from atherosclerosis-associated bacteria antagonize TLR4, induce formation of TLR2/1/CD36 complexes in lipid rafts and trigger TLR2-induced inflammatory responses in human vascular endothelial cells. 1741 16

Apoptosis is an important mechanism involved in regulating the number of macrophages present at sites of inflammation. Several lines of evidence indicate that blocking macrophage apoptosis can increase atherosclerosis. We previously reported that oxidized LDL can inhibit apoptosis in cultured bone marrow-derived macrophages. We used pertussis toxin (PTX) to test whether G protein coupled receptors are activated by oxLDL. PTX is a bacterial toxin that inhibits Gi activation by ADP-ribosylating the alpha subunit of Gi, preventing the subunit from interacting with receptors. Unexpectedly, we found that PTX by itself selectively blocks macrophage apoptosis in a dose-dependent manner. PTX acts in part by inhibiting acid sphingomyelinase activity which in turn prevents generation of ceramide, which is required for macrophage apoptosis. A Gi activator peptide, mastoparan, increased ceramide levels in macrophage and induced apoptosis, but pre-treatment with PTX partially overrode mastoparan-induced apoptosis. The anti-apoptotic effect of PTX was found to require ADP-ribosylation. PTX failed to prevent A-SMase activation or apoptosis in macrophages lacking TLR4. The anti-apoptotic effect of PTX involved the same signaling pathways as those of oxidized LDL, in that both inhibited acid sphingomyelinase, and activated the phosphoinositide 3 kinase (PI3K)/protein kinase B (PKB) pathway which leads to nuclear localization of the transcription factor NFkappaB and up-regulation of Bcl-XL. These results indicate that Gi proteins, TLR4, A-SMase and the PI3K/PKB pathway are crucial components for regulation of macrophage apoptosis.
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PMID:Pertussis toxin promotes macrophage survival through inhibition of acid sphingomyelinase and activation of the phosphoinositide 3-kinase/protein kinase B pathway. 1752 84

Inflammation and immune reactions are implicated in atherogenesis and plaque disruption. The precise triggers for inflammation in atherosclerosis are not fully understood but may include hypercholesterolemia, modified lipoproteins and local or distant infections. TLRs play an important role in the innate and inflammatory signaling responses to microbial agents. Evidence from diverse sources has suggested that TLRs can affect atherosclerosis in multiple ways. Several reports have documented the expression of TLRs in atherosclerotic lesions and suggested that the TLR-NF-kappa B pathway is activated in the lesion, resulting in the transcription of a variety of genes involved in the inflammatory and proliferative responses of cells critical to atherogenesis and ultimately leading to the synthesis and release of antimicrobial peptides and inflammatory cytokines that provide a critical link to adaptive immunity. Moreover, TLR4 expression in macrophages is up-regulated by oxidized LDL, which suggests a potential mechanism for the synergistic effects of hypercholesterolemia and infection in acceleration of atherosclerosis. These findings indicate that TLRs provide additional new insights into the link among lipids, infection/inflammation and atherosclerosis, thus may be effective therapeutic target molecules. We speculate that TLRs are important for the development and progression of atherosclerosis, and hence blocking the expression of TLRs may serve as new targets for antiatherogenic therapy.
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PMID:TLRs are important inflammatory factors in atherosclerosis and may be a therapeutic target. 1768 3

Toll-like receptors (TLRs) are a group of pathogen-associated molecular pattern receptors, which play an important role in innate immune signaling in response to microbial infection. It has been demonstrated that TLRs are differentially up regulated in response to microbial infection and chronic inflammatory diseases such as atherosclerosis. The expression of TLRs are markedly augmented in human atherosclerotic lesions and this occurs preferentially by endothelial cells and macrophages in areas infiltrated with inflammatory cells. Furthermore polymorphisms in the human gene encoding one TLR receptor (TLR4) which attenuates receptor signaling and diminishes the inflammatory response to gram-negative pathogens, is associated with low levels of certain circulating mediators of inflammation and a decreased risk for atherosclerosis in humans. Recent advances have established a fundamental role for inflammation in mediating all stages of atherosclerosis. However, the triggers that initiate and sustain the inflammatory process have not been definitively identified. Although definitive proof of a role of infection contributing to atherogenesis is lacking, multiple investigations have demonstrated that infectious agents evoke cellular and molecular changes supportive of such a role. Evidence in humans suggesting that periodontal infection predisposes to atherosclerosis is derived from studies demonstrating that the periodontal pathogen Porphyromonas gingivalis resides in the wall of atherosclerotic vessels and seroepidemiological studies demonstrating an association between pathogen-specific IgG antibodies and atherosclerosis. Our recent work with P. gingivalis has demonstrated the effectiveness of specific intervention strategies (immunization) in the prevention of pathogen-accelerated atherosclerosis. We have also established that the inflammatory signaling pathways that P. gingivalis utilizes is dependent on the cell type and this specificity clearly influences innate immune signaling in the context of local chronic inflammation versus distant chronic inflammation. We postulate that bacterial infection mediates inflammatory responses that involve specific innate immune pathways in defined host cells. Furthermore, these inflammatory responses can be correlated with atherosclerosis and ultimately thrombotic complications.
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PMID:Engagement of specific innate immune signaling pathways during Porphyromonas gingivalis induced chronic inflammation and atherosclerosis. 1798 90

Toll-like receptors (TLRs) initiate and maintain host defenses and inflammation, and directly contribute to diseases such as atherosclerosis. It is not completely understood in what cell types proatherogenic TLR-induced signaling arises and, particularly, there is uncertainty regarding the potential functional role of TLR2 in endothelial cells (ECs). We determined TLR2 and TLR4 gene expression in four different human and two different murine primary ECs using gene array analysis, RT-PCR, and flow cytometry and confirmed these data by functional studies by stimulating ECs with the corresponding TLR ligands. TLR4 was expressed in all human and murine ECs and these cells responded to stimulation with LPS. Faint expression of TLR2 was observed in human ECs, whereas murine ECs express considerable amounts of TLR2 mRNA. Human ECs failed to respond to TLR2 ligands while murine ECs responded to TLR2 ligands. Furthermore, in murine ECs, TLR2 was located on the cell surface while in human ECs, TLR2 was sequestered in intracellular compartments. After IFN-gamma or IL-1beta stimulation, TLR2 translocated to the cell surface of human ECs. In conclusion, TLR2 is expressed intracellularly in human ECs and, therefore, TLR2 ligands are inaccessible to the receptor. Murine ECs express membrane TLR2 and respond to TLR2 ligands, but human ECs normally will not respond unless they are first primed with inflammatory stimulation, which appears to trigger translocation of TLR2 to the cell surface.
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PMID:Differential expression of Toll-like receptor 2 (TLR2) and responses to TLR2 ligands between human and murine vascular endothelial cells. 1798 87

The total burden of infection at various sites may affect the progression of atherosclerosis and Alzheimer's disease (AD), the risk being modulated by host genotype. The role of lipopolysaccharide (LPS) receptor TLR4 is paradigmatic. It initiates the innate immune response against gram-negative bacteria, and TLR4 single nucleotide polymorphisms (SNPs), such as +896A/G, known to attenuate receptor signaling, have been described. This SNP shows a significantly lower frequency in patients affected by myocardial infarction or AD. Thus, people genetically predisposed to developing lower inflammatory activity seem to have less chance of developing cardiovascular disease (CVD) or AD. In the present report, to validate this hypothesis, the levels of the eicosanoids, leukotriene B4 (LTB4) and prostaglandin E2 (PGE2), known to be involved as mediators in age-related diseases, were determined by an enzyme-linked immunosorbent assay in supernatants from a whole blood assay, after stimulation with subliminal doses of LPS from Escherichia coli. The samples, genotyped for the +896A/G SNP, were challenged with LPS for 4, 24, and 48 h. Both LTB4 and PGE2 values were significantly lower in carriers bearing the TLR4 mutation. Therefore, the pathogen burden, by interacting with the host genotype, determines the type and intensity of the inflammatory responses accountable for proinflammatory status, CVD, AD, and unsuccessful aging (i.e., age-related inflammatory diseases).
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PMID:Role of TLR4 polymorphisms in inflammatory responses: implications for unsuccessful aging. 1805 68

Toll-like receptor 4 (TLR4) is a pattern recognition receptor for lipopolysaccharide from Gram negative bacteria and thus is integral to the innate immune response in mammals. In addition, TLR4 is associated with atherosclerosis in murine models. The current study shows that blood vessels from TLR4(-/-) mice have an intact endothelial layer and comparable expression of nitric oxide synthase 3 protein. However, endothelium-dependent dilation in response to acetylcholine in vessels from TLR4(-/-) mice is greatly reduced. By contrast, endothelium-independent smooth muscle dilation in response to sodium nitroprusside in vessels from TLR4(-/-) mice remains intact. Furthermore, this study shows that hearts from TLR4(-/-) mice display signs of left ventricular dilation. In contrast to results in vessels from TLR4(-/-) mice, endothelium-dependent responses to acetylcholine in vessels from TLR2(-/-) mice remain intact. These observations illustrate a novel role for TLR4 in the homeostatic control of a functional endothelium and, thereby, cardiovascular health.
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PMID:Homeostatic role of Toll-like receptor 4 in the endothelium and heart. 1817 27

At one time, atherosclerosis was thought to be a simple lipid storage disease. However, it is now recognized as a chronic and progressive inflammation of the arterial wall. Gene deletion experiments in murine models of atherosclerosis that reduce the inflammatory process also reduce disease severity. Identifying the initiators and mediators of that inflammation can provide promising avenues for prevention or therapy. Two prominent risk factors, hyperlipidemia and infectious disease, point to innate immune mechanisms as potential contributors to proatherogenic inflammation. The Toll-like receptors (TLR), proinflammatory sensors of pathogens, are potential links between inflammation, infectious disease and atherosclerosis. There is increasing evidence that TLRs also recognize host-derived ligands and this also connects TLRs to diseases that may not have an etiology that is associated directly with infection. A mechanism for hyperlipidemic initiation of sterile inflammation can be postulated because oxidized lipoproteins or their component oxidized lipids have been identified as TLR ligands. Moreover, infectious agents are correlated with atherosclerosis risk. There are multiple published reports that TLR4 activation is relevant to the inflammation of atherosclerosis in mice and humans. In addition, we have identified a role for TLR2 in atherosclerosis in low density lipoprotein receptor-deficient (LDLr-/-) mice. Proatherogenic TLR2 responses to unknown endogenous or unknown endemic exogenous agonists are mediated by non-bone marrow-derived cells, which can include endothelial cells, adventitial fibroblasts and vascular smooth muscle cells. This is in contrast to the proatherogenic TLR2 response to defined synthetic exogenous agonists, which is mediated at least in part by bone marrow-derived cells, which can include lymphocytes, monocytes/macrophages, NK cells and dendritic cells. Thus, TLR2-mediated cell activation in response to endogenous and exogenous agents is proatherogenic in hyperlipidemic mice.
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PMID:The toll of Toll-like receptors, especially toll-like receptor 2, on murine atherosclerosis. 1822 Jul

Toll-like receptors (TLRs) are a group of pathogen-associated molecular pattern receptors, which play an important role in innate immune signaling in response to microbial infection. It has been demonstrated that TLRs are differentially up regulated in response to microbial infection and chronic inflammatory diseases such as atherosclerosis. Furthermore hyperlipidemic mice deficient in TLR2, TLR4, and MyD88 signaling exhibit diminished inflammatory responses and decreased atherosclerosis. Accumulating evidence has implicated specific infectious agents including the periodontal disease pathogen Porphyromonas gingivalis in the progression of atherosclerosis. Evidence in humans suggesting that periodontal infection predisposes to atherosclerosis is derived from studies demonstrating that the periodontal pathogen P. gingivalis resides in the wall of atherosclerotic vessels and seroepidemiological studies demonstrating an association between pathogen-specific IgG antibodies and atherosclerosis. We have established that the inflammatory signaling pathways that P. gingivalis utilizes is dependent on the cell type and this specificity clearly influences innate immune signaling in the context of local and distant chronic inflammation induced by this pathogen. We have demonstrated that P. gingivalis requires TLR2 to induce oral inflammatory bone lose in mice. Furthermore, we have demonstrated that P. gingivalis infection accelerates atherosclerosis in hyperlipidemic mice with an associated increase in expression of TLR2 and TLR4 in atherosclerotic lesions. Our recent work with P. gingivalis has demonstrated the effectiveness of specific intervention strategies (immunization) in the prevention of pathogen-accelerated atherosclerosis. Improved understanding of the mechanisms driving infection, and chronic inflammation during atherosclerosis may ultimately provide new targets for therapy.
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PMID:Porphyromonas gingivalis mediated periodontal disease and atherosclerosis: disparate diseases with commonalities in pathogenesis through TLRs. 1822 Aug 4

Chlamydia pneumoniae is a common respiratory pathogen, which activates macrophages to induce inflammatory cytokines that may promote atherosclerosis. However, the antigens that induce macrophage activation have not been well defined. In the current study, three chlamydial proteins which are recognized during human infection, outer membrane protein 2 (OMP2) and two 53-kDa proteins (Cpn 0980 and Cpn 0809), were investigated to determine whether they activate macrophages and, if they do, what mechanism they use for this activation. It was shown that these three proteins could (i) induce expression of tumor necrosis factor alpha (TNF-alpha) and tissue factor and (ii) induce phosphorylation of p44/42 mitogen-activated protein kinases (MAPK) and activation of early growth response factor 1 (Egr-1). Control proteins, the N-terminal fragment of polymorphic membrane protein 8 and the thioredoxin portion of the fusion protein, had no effect on macrophages. Treatment of cells with a MEK1/2 inhibitor, U0126, dramatically reduced the phosphorylation of ERK, activation of Egr-1, and expression of TNF-alpha in macrophages treated with recombinant proteins. Toll-like receptors (TLRs) act as sensors for microbial antigens and can signal via the MAPK pathway. Chlamydial protein-induced expression of TNF-alpha was significantly reduced in macrophages lacking TLR2 or TLR4. These findings suggest that C. pneumoniae may activate macrophages through OMP2, Cpn 0980, and Cpn 0809 in addition to cHSP60 and that activation occurs via TLR2 or TLR4, Egr-1, and MAPK pathways.
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PMID:Identification and characterization of Chlamydia pneumoniae-specific proteins that activate tumor necrosis factor alpha production in RAW 264.7 murine macrophages. 1822 57


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