Low-level endotoxin induces potent inflammatory activation of human blood vessels: inhibition by statins

Hydroethidine- and MitoSOX-derived red fluorescence is not a reliable indicator of intracellular superoxide formation: another inconvenient truth

Hydroethidine (HE; or dihydroethidium) is the most popular fluorogenic probe used for detecting intracellular superoxide radical anion. The reaction between superoxide and HE generates a highly specific red fluorescent product, 2-hydroxyethidium (2-OH-E(+)). In biological systems, another red fluorescent product, ethidium, is also formed, usually at a much higher concentration than 2-OH-E(+). In this article, we review the methods to selectively detect the superoxide-specific product (2-OH-E(+)) and the factors affecting its levels in cellular and biological systems. The most important conclusion of this review is that it is nearly impossible to assess the intracellular levels of the superoxide-specific product, 2-OH-E(+), using confocal microscopy or other fluorescence-based microscopic assays and that it is essential to measure by HPLC the intracellular HE and other oxidation products of HE, in addition to 2-OH-E(+), to fully understand the origin of red fluorescence. The chemical reactivity of mitochondria-targeted hydroethidine (Mito-HE, MitoSOX red) with superoxide is similar to the reactivity of HE with superoxide, and therefore, all of the limitations attributed to the HE assay are applicable to Mito-HE (or MitoSOX) as well.

Aggregation and microparticle production through toll-like receptor 4 activation in platelets from recently menopausal women

Bacterial infection may increase risk for thrombosis and atherosclerosis. Human platelets express toll-like receptor 4 (TLR4), the receptor for gram-negative bacterial lipopolysaccharide (LPS). Experiments were designed to evaluate direct, acute effects of TLR4 activation on aggregation, secretion, and generation of prothrombogenic microparticles in vitro on platelets derived from healthy women at risk for development of cardiovascular disease because of their hormonal status. Platelet-rich plasma from recently menopausal women was incubated with ultrapure Escherichia coli LPS in the absence or presence of antibodies that neutralize the human TLR4. Incubating platelets with LPS (100 ng/mL) for 5 minutes decreased aggregation and dense granule adenosine triphosphate secretion induced by thrombin receptor agonist peptide (TRAP) but not by adenosine diphosphate or collagen. The antibody to TLR4 blocked this effect of LPS. TLR4 activation increased phosphorylation of p38 mitogen-activated protein kinase and decreased production of prothrombotic phosphatidylserine and P-selectin-positive microparticles in response to TRAP. Therefore, acute, direct activation of TLR4 reduces platelet reactivity to TRAP stimulation in vitro. Increased thrombotic and cardiovascular risk with bacterial infection most likely reflects the sum of TLR4 activation on other blood and vascular cells to release proinflammatory cytokines/chemokines, which indirectly affect platelet reactivity.

Rho proteins are negative regulators of TLR2, TLR3, and TLR4 signaling in astrocytes

The family of Toll-like receptors (TLRs) expressed by innate immune cells recognizes a spectrum of microbial components as well as molecules released from injured tissues. TLR ligation activates intracellular signaling cascades that culminate in the up-regulation of proinflammatory genes. We have recently demonstrated that the up-regulation of inflammatory cytokines mediated by TLR4 in astrocytes is negatively controlled by the monomeric GTPases of Rho subfamily. The present study was undertaken to examine further the involvement of Rho proteins in the inflammatory response of astrocytes elicited by the ligation of three TLRs that use divergent signaling pathways. Astrocyte cultures established from newborn rat brains were challenged with ligands of TLR2, TLR3, and TLR4. The expression of genes encoding interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha (TNFalpha), interferon-beta (IFNbeta), and inducible nitric oxide synthase (NOS2) was up-regulated 24 hr after the challenge as determined by real-time RT-PCR. Pretreatment of the cells with toxin B, which specifically inactivates Rho proteins, enhanced the up-regulation of gene expression. The extent of this enhancement was both receptor and gene dependent. The enhancing effect of Rho protein inactivation was also evident at the protein level of IL-6 and NOS2 as revealed by ELISA and immunoblot analyses, respectively. These results suggest that Rho proteins control TLR-mediated up-regulation of inflammatory genes in astrocytes by interfering with multiple events along the signaling pathways.

Immune system and atherosclerotic disease: heterogeneity of leukocyte subsets participating in the pathogenesis of atherosclerosis

Atherosclerosis is an inflammatory disease in which a systemic inflammatory reaction is combined with an accumulation of immune cells, such as monocytes/macrophages, dendritic cells (DCs), and numerous lymphocytes, in atherosclerotic plaques. The immune system, comprising innate immunity and adaptive immunity, has been implicated in all stages of atherosclerosis, from initiation through progression and in atherothrombotic complications. It is clear that different subpopulations of leukocytes are involved in the pathogenesis of atherosclerosis and plaque instability. Recent studies have also demonstrated that each heterogeneity of immune-associated cells contributes to the atherogenic and atheroprotective axis. This review highlights recent advances in research and explores the role of the complex heterogeneity of leukocyte subsets, especially monocytes/macrophages (inflammatory monocytes, resident monocytes, M1, and M2), DCs (myeloid DCs, plasmacytoid DCs, pre DCs, conventional DCs, inflammatory DCs), and CD4(+) cells (T-helper 1, T-helper 2, regulatory T, and T-helper 17 cells), in the initiation and development of atherosclerotic disease and its complications.

Prolonged exposure to LPS increases iron, heme, and p22phox levels and NADPH oxidase activity in human aortic endothelial cells: inhibition by desferrioxamine

OBJECTIVE

Vascular oxidative stress and inflammation are contributing factors in atherosclerosis. We recently found that the iron chelator, desferrioxamine (DFO), suppresses NADPH oxidase-mediated oxidative stress and expression of cellular adhesion molecules in mice treated with lipopolysaccharide (LPS). The objective of the present study was to investigate whether and how LPS and iron enhance, and DFO inhibits, NADPH oxidase activity in human aortic endothelial cells (HAECs).

METHODS AND RESULTS

Incubation of HAECs for 24 hours with 5 microg/mL LPS led to a 4-fold increase in NADPH oxidase activity, which was strongly suppressed by pretreatment of the cells for 24 hours with 100 micromol/L DFO. Incubating HAECs with LPS also significantly increased cellular iron and heme levels and mRNA and protein levels of p22phox, a heme-containing, catalytic subunit of NADPH oxidase. All of these effects of LPS on HAECs were strongly inhibited by DFO. Exposing HAECs to 100 micromol/L iron (ferric citrate) for 48 hours exerted similar effects as LPS, and these effects were strongly inhibited by coincubation with DFO. Furthermore, neither LPS nor DFO affected mRNA and protein levels of p47phox a nonheme-containing, regulatory subunit of NADPH oxidase, or the mRNA level of NOX4, an isoform of the principal catalytic subunit of NADPH oxidase in endothelial cells. In contrast, heme oxygenase-1 was strongly suppressed by DFO, both in the absence and presence of LPS or iron.

CONCLUSIONS

Our data indicate that prolonged exposure to LPS or iron increases endothelial NADPH oxidase activity by increasing p22phox gene transcription and cellular levels of iron, heme, and p22phox protein. Iron chelation by DFO effectively suppresses endothelial NADPH oxidase activity, which may be helpful as an adjunct in reducing vascular oxidative stress and inflammation in atherosclerosis.

Toll-like receptor modulation: a novel therapeutic strategy in cardiovascular disease?

BACKGROUND

Toll-like receptors (TLRs) have been recently recognised as primary receptors in the innate immune system. Apart from initiating a prompt immune response against invading pathogens, TLRs are also considered to be an important link between innate immunity, inflammation and a variety of clinical disorders, including cardiovascular diseases. TLR signalling manipulation with novel drugs could offer important opportunities for cardiovascular disease modification.

OBJECTIVE

To present the latest knowledge supporting the involvement of TLRs in the pathogenesis and progress of cardiovascular diseases and explore the role of TLRs as potential targets for therapeutic intervention in cardiovascular territory.

METHODS

A review of the literature documenting implication of TLR signalling in cardiovascular disorders. Current progress in TLR-targeting drug development and the potential role of such a treatment strategy in cardiovascular disorders are discussed.

CONCLUSIONS

A growing body of evidence supports a role for TLRs in cardiovascular disease initiation and progression. Altering TLR signalling with novel drugs could be a beneficial therapeutic strategy for patients with cardiovascular disorders.

Statins inhibit toll-like receptor 4-mediated lipopolysaccharide signaling and cytokine expression

OBJECTIVE

Toll-like receptor 4 (TLR4) is the main receptor for Lipopolysaccharide (LPS). Two relatively common variants of the TLR4 gene are present, resulting in changes from aspartic acid (D) to glycine (G) at residue 299 and from threonine (T) to isoleucine (I) at residue 399, respectively. It has been shown that statins have a greater effect on lowering risk of cardiovascular events in individuals carrying the 299G allele than in those not carrying this allele. We investigated possible mechanisms underlying this synergy of statin treatment and TLR4 genotype.

METHODS AND RESULTS

In cells expressing the 299D-399T TLR4, LPS activated the transcription factor NFkappaB and increased the expression of interleukin-6 and tumor necrosis factor-alpha, and these effects were reduced by pretreatment of the cells with pravastatin or simvastatin. LPS-induced NFkappaB activation and interleukin-6 and tumor necrosis factor-alpha expression were substantially reduced in cell expressing the 299G-399T or 299D-399I variant, and undetectable in cells expressing the 299G-399I TLR4. The 3-hydroxy-3-methylglutaryl coenzyme A pathway inhibitors, Y27632 and GGTI-286, exhibited a similar effect to statins, suggesting that the inhibitory effect of statins was mediated by the 3-hydroxy-3-methylglutaryl coenzyme A pathway.

CONCLUSION

The results of this study indicate that the TLR4 variations and statins have an additive inhibitory effect on TLR4-mediated inflammatory response, providing a potential explanation for the finding that the beneficial effect of statins on cardiovascular risk is dependent on TLR4 genotype.

Surfactant protein D is expressed and modulates inflammatory responses in human coronary artery smooth muscle cells

Surfactant protein D (SP-D) is a constituent of the innate immune system that plays a role in the host defense against lung pathogens and in modulating inflammatory responses. While SP-D has been detected in extrapulmonary tissues, little is known about its expression and function in the vasculature. Immunostaining of human coronary artery tissue sections demonstrated immunoreactive SP-D protein in smooth muscle cells (SMCs) and endothelial cells. SP-D was also detected in isolated human coronary artery SMCs (HCASMCs) by PCR and immunoblot analysis. Treatment of HCASMCs with endotoxin (LPS) stimulated the release of IL-8, a proinflammatory cytokine. This release was inhibited >70% by recombinant SP-D. Overexpression of SP-D by adenoviral-mediated gene transfer in HCASMCs inhibited both LPS- and TNF-alpha-induced IL-8 release. Overexpression of SP-D also enhanced uptake of Chlamydia pneumoniae elementary bodies into HCASMCs while attenuating IL-8 production induced by bacterial exposure. Both LPS and TNF-alpha increased SP-D mRNA levels by five- to eightfold in HCASMCs, suggesting that inflammatory mediators upregulate the expression of SP-D. In conclusion, SP-D is expressed in human coronary arteries and functions as an anti-inflammatory protein in HCASMCs. SP-D may also participate in the host defense against pathogens that invade the vascular wall.

Toll-like receptors in atherosclerosis

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, hyperlipidaemia and infectious disease, point to innate immune mechanisms as potential contributors to proatherogenic inflammation. The TLRs (Toll-like receptors), pro-inflammatory sensors of pathogens, are potential links between inflammation, infectious disease and atherosclerosis. A mechanism for hyperlipidaemic 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. We have identified a role for TLR2 in atherosclerosis in mice deficient in low-density lipoprotein receptor. We observed that proatherogenic TLR2 responses to unknown endogenous or unknown endemic exogenous agonists are mediated by non-BMDC (bone-marrow-derived cells), which can include endothelial cells. In contrast, the proatherogenic TLR2 responses to the defined synthetic exogenous agonist Pam3 CSK4 are mediated at least in part by BMDC, which can include lymphocytes, monocytes/macrophages and dendritic cells. TLR2-mediated cell activation in response to endogenous and exogenous agents is proatherogenic in hyperlipidaemic mice.

Endotoxemia is related to systemic inflammation and atherosclerosis in peritoneal dialysis patients

BACKGROUND AND OBJECTIVES

Systemic inflammatory state is a hallmark of peritoneal dialysis (PD) patients, but its etiology remains obscure. Because circulating microbial products are an important cause of systemic immune activation in other conditions such as HIV infection, it was hypothesized that endotoxemia is a cause of systemic inflammatory state and atherosclerosis in PD patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Plasma lipopolysaccharide (LPS) levels in 30 consecutive new PD patients were measured. The result was compared with serum C-reactive protein (CRP) level, peritoneal transport status, history of pre-existing cardiovascular diseases, and carotid intima media thickness (IMT) by Doppler ultrasound.

RESULTS

Among the 30 PD patients, there were 17 men. The average age was 53.7 +/- 15.1 yr. The average endotoxin concentration of PD patients was 0.44 +/- 0.18 EU/ml, which was significantly higher than that of patients with chronic kidney disease secondary to Ig-A nephropathy (IgAN) (0.035 +/- 0.009 EU/ml, P < 0.0001) and the controls (0.013 +/- 0.007 EU/ml, P < 0.0001). In PD patients, plasma LPS concentration had a significant correlation with serum CRP (r = 0.415, P = 0.025) and serum albumin level (r = -0.394, P = 0.034). In contrast, plasma LPS level did not correlate with Charlson's Comorbidity Index, peritoneal transport characteristics, or nutritional indices. Patients with pre-existing cardiovascular disease (CVD) had higher plasma LPS level than those without CVD (0.53 +/- 0.19 versus 0.36 +/- 0.16 EU/ml, P = 0.016). Plasma LPS level correlated with carotid IMT (r = 0.438, P = 0.016).

CONCLUSIONS

It was found that endotoxemia was probably common in PD patients, and the degree of circulating endotoxemia might be related to the severity of systemic inflammation and features of atherosclerosis. This result suggests that endotoxemia may have a contributory role to the systemic inflammatory state and accelerated atherosclerosis in PD patients.

Statins enhance toll-like receptor 4-mediated cytokine gene expression in astrocytes: Implication of Rho proteins in negative feedback regulation

Toll-like receptors (TLRs) are sentinels of innate immunity that recognize pathogenic molecules and trigger inflammatory response. Because inflammatory mediators are detrimental to the host, the TLR response is regulated by feedback inhibition. Statins, the inhibitors of isoprenoid biosynthesis, have been shown to be potent modulators of TLR activity, and this modulation may provide insight regarding mechanisms of the feedback inhibition. In the present study, we examined feedback mechanisms that regulate TLR4 activity in astrocytes using statins to perturb postligational signaling. Astrocytic cultures established from newborn rat brains were exposed to lipopolysaccharide (LPS), the ligand for TLR4. The up-regulation of expression of genes encoding interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNFalpha) was determined by real-time RT-PCR. Pretreatment of the cells with either atorvastatin or simvastatin enhanced the LPS-induced up-regulation of cytokine gene expression. The most profound enhancement of approximately 17-fold was observed for the Il-6 gene. The enhancements for the Tnfa and Il-1b genes were approximately 5- and 3.5-fold, respectively. Mevalonate fully reversed the effects of statins, indicating that these drugs act through the inhibition of isoprenoid synthesis. The inhibition of protein geranylgeranylation, but not protein farnesylation, mimicked the effects of statins, strongly indicating that the enhancement is mediated by the Rho proteins. In support of this notion, pretreatment of cells with toxin B, a specific inhibitor of the Rho proteins, also enhanced LPS-triggered up-regulation of the cytokine genes. These results indicate that the Rho proteins are involved in the activation of negative feedback inhibition of TLR4 signaling in astrocytes.

A high-fat meal induces low-grade endotoxemia: evidence of a novel mechanism of postprandial inflammation

BACKGROUND

Bacterial endotoxin is a potently inflammatory antigen that is abundant in the human gut. Endotoxin circulates at low concentrations in the blood of all healthy individuals, although elevated concentrations are associated with an increased risk of atherosclerosis.

OBJECTIVE

We sought to determine whether a high-fat meal or smoking increases plasma endotoxin concentrations and whether such concentrations are of physiologic relevance.

DESIGN

Plasma endotoxin and endotoxin neutralization capacity were measured for 4 h in 12 healthy men after no meal, 3 cigarettes, a high-fat meal, or a high-fat meal with 3 cigarettes by using the limulus assay.

RESULTS

Baseline endotoxin concentrations were 8.2 pg/mL (interquartile range: 3.4-13.5 pg/mL) but increased significantly (P < 0.05) by approximately 50% after a high-fat meal or after a high-fat meal with cigarettes but not after no meal or cigarettes alone. These results were validated by the observations that a high-fat meal with or without cigarettes, but not no meal or smoking, also significantly (P < 0.05) reduced plasma endotoxin neutralization capacity, which is an indirect measure of endotoxin exposure. Human monocytes, but not aortic endothelial cells, were responsive to transient (30 s) or low-dose (10 pg/mL) exposure to endotoxin. However, plasma from whole blood treated with as little as 10 pg endotoxin/mL increased the endothelial cell expression of E-selectin, at least partly via tumor necrosis factor-alpha-induced cellular activation.

CONCLUSIONS

Low-grade endotoxemia may contribute to the postprandial inflammatory state and could represent a novel potential contributor to endothelial activation and the development of atherosclerosis.

Human postmortem brain-derived cerebrovascular smooth muscle cells express all genes of the classical complement pathway: a potential mechanism for vascular damage in cerebral amyloid angiopathy and Alzheimer's disease

Deposition of amyloid around blood vessels, known as cerebral amyloid angiopathy (CAA), is a major pathological feature found in the majority of Alzheimer's disease (AD) cases, and activated complement fragments have been detected on CAA deposits in AD brains. In this study, we demonstrate for the first time that human cerebrovascular smooth muscle cells (HCSMC) isolated from cortical vessels derived from postmortem brains can express mRNAs for complement genes C1qB, C1r, C1s, C2, C3, C4, C5, C6, C7, C8 and C9, the components of the classical complement pathway. Secretion of the corresponding complement proteins for these genes was also demonstrated, except for C1q and C5. Of particular significance was the observation that treatment of HCSMC with aggregated amyloid beta (Abeta) 1-42 increased expression of complement C3 mRNA and increased release of C3 protein. Abeta treatment of HCSMC also increased expression of C6 mRNA. Interferon-gamma induced expression and release of complement C1r, C1s, C2 and C4. As HCSMC are closely associated with Abeta deposits in vessels in the brain, their production of complement proteins could amplify the proinflammatory effects of amyloid in the perivascular environment, further compromising brain vascular integrity.

Statins can be the potential therapeutic agents for reducing infection evoked cholangiopathy after liver transplantation?

Biliary infection, including bacteria and cytomegalovirus (CMV), can induce inflammatory response and lead to bile duct damage after liver transplantation. This process may involve a major class of pattern recognition receptors-TLRs (Toll-like receptors). Stimulation of these receptors by pathogens (CMV, bacteria, etc.) in bile duct can induce the secretion of a series of cytokines/chemokines mainly via a TLR-2/4-MyD88-dependent pathway. Strategies for prevention and treatment of biliary infection, such as selective digestive decontamination (SDD) and preemptive therapy with gancyclovir and antibiotics are not so satisfactory. Statin, a HMG-CoA reductase inhibitor, have special anti-inflammatory abilities. They can inhibit the expression of TLR-4 and TLR-2, and block the signaling pathways of LPS (TLR-2/4), virus-encoded envelope proteins (TLR-2) and HSP70 (TLR-2/4), This process can lead to a reduction of effector cytokines/chemokines. In addition, statins can suppress the replication of CMV by reducing NF-kappaB binding activity. We hypothesized that statins can be useful for reducing infection evoked cholangiopathy after liver transplantation. We provide reliable evidence supporting the hypothesis and offer proposals for future application.

Beneficial effects of statins on the microcirculation during sepsis: the role of nitric oxide

This review describes the laboratory evidence and microvascular mechanisms responsible for the beneficial effects of statins in sepsis. During sepsis, changes occur within the microcirculation including alterations in arteriolar tone influencing blood pressure, adaptations to endothelial cell integrity causing leakage of proteins and macromolecules, and adhesion and migration of leucocytes through the vascular endothelium. Statins are widely used as cholesterol-lowering agents, but appear to have anti-inflammatory actions during sepsis. We have discussed the effects of statins on specific pathological processed within the microcirculation and focused on the role of nitric oxide (NO). The main mechanism by which statins appear to be an effective treatment for sepsis is increased expression of endothelial nitric oxide synthase (eNOS), in conjunction with down-regulation of inducible nitric oxide synthase. Combined, this results in an increase in physiological concentrations of NO, thus restoring endothelial function. Laboratory studies have therefore suggested that enhancement of eNOS activity during sepsis may lead to restoration of microvascular tone, maintenance of microvascular integrity, and inhibition of cell adhesion molecules. However, other mechanisms independent of lipid-lowering effects, including antioxidant activity and alterations in the development of vascular atherosclerosis, may also contribute to the beneficial effects of statins. We have also addressed the influence on the effects of statins of lipid solubility and pre- and pro-phylactic administration.

Generation of superoxide anion by equine spermatozoa as detected by dihydroethidium

Low-level production of the superoxide anion (O2*-) is an important signal transduction event in sperm function including capacitation; however, excessive production of O2*- can be detrimental to sperm function. The objective of this study was to assess dihydroethidium (DHE) as a probe for O2*- in equine spermatozoa. Ejaculated spermatozoa were separated by centrifugation over a Percoll gradient (40:80), and loaded with DHE (2.0 microM) as well as with calcein-acetoxymethylester (CAM, 7.8 nM) to determine cell viability. In Experiment 1, cells were incubated with the xanthine-xanthine oxidase (X, 0.1 mM; XO, 0.01 U/mL) generating system for the production of O2*-, with or without the addition of superoxide dismutase (SOD, 150 U/mL) or the SOD mimetic, Tiron (0.1, 1.0 or 5.0 mM) for 1h. Changes in fluorescence of DHE were determined for the live cell population (calcein-positive cells) by flow cytometry. The DHE fluorescence increased with the X-XO incubation; this increase was inhibited by SOD or Tiron, indicating that DHE is specific for O2*- detection. In Experiment 2, spermatozoa were loaded with DHE/CAM, treated with calcium ionophore A23187 (0, 0.8, or 8.0 microM), and incubated for 15 min. Cell fluorescence was again determined by flow cytometry. Calcium ionophore A23187 increased O2*- production in a dose-dependent manner. In Experiment 3, cells were loaded with DHE/CAM, treated with NADPH (0.0, 0.25, 0.5, or 1 mM) with or without 0.5% Triton X-100, and incubated for 15 min prior to flow cytometry. Cells treated with NADPH with or without 0.5% Triton X-100 did not have O2*- levels that were significantly different from the control. In Experiment 4, spermatozoa loaded with DHE/CAM were incubated under capacitating conditions (1.2 mM dibutryl-cAMP+1.0 mM caffeine) or in control media for 3h. Although O2*- generation increased over time in control and capacitated treatments, spermatozoa incubated under capacitating conditions had higher O2*- production than those incubated in control media. Therefore, DHE was a useful probe for the detection of O2*- in equine spermatozoa and elevation in intracellular calcium as well as capacitation in vitro were associated with increased generation of O2*-.

Endotoxin induces toll-like receptor 4 expression in vascular smooth muscle cells via NADPH oxidase activation and mitogen-activated protein kinase signaling pathways

OBJECTIVE

Toll-like receptor 4 (TLR4) plays a major role mediating endotoxin-induced cellular inflammation and regulates vascular smooth muscle cell (VSMC) proliferation, which is related to atherogenesis and restenosis. This study was conducted to investigate the mechanisms involved in lipopolysaccharide (LPS)-induced TLR4 expression in VSMCs.

METHODS AND RESULTS

Stimulation of human aortic smooth muscle cells (HASMCs) with LPS significantly increased TLR4 expression. The increase was regulated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (including the activation of subunits p47(phox) and Rac1), which mediates the production of reactive oxygen species and the activation of intracellular mitogen-activated protein kinase signaling pathways. Treatment with polyethylene-glycol-conjugated superoxide dismutase, N-acetylcysteine (NAC), diphenylene iodonium (DPI), or apocynin significantly decreased LPS-induced TLR4 expression. An actinomycin D chase experiment showed that LPS increased the half-life of TLR4 mRNA. Inhibition of NADPH oxidase activity by DPI, apocynin, or NAC significantly decreased TLR4 mRNA stability, as did the knock-down of RAC1 gene expression by RNA interference. We also demonstrated in an animal model that LPS administration led to a significant elevation of balloon-injury-induced neointimal hyperplasia, and of TLR4 expression, in rabbit aorta.

CONCLUSIONS

These findings suggest that NADPH oxidase activation, mRNA stabilization, and MAPK signaling pathways play critical roles in LPS-enhanced TLR4 expression in HASMCs, which contributes to vascular inflammation and cardiovascular disorders.

The role of human antigen R, an RNA-binding protein, in mediating the stabilization of toll-like receptor 4 mRNA induced by endotoxin: a novel mechanism involved in vascular inflammation

OBJECTIVE

Lipopolysaccharide (LPS) interacts with toll-like receptor 4 (TLR4) and induces proliferation of vascular smooth muscle cells (VSMCs) which plays a causal role in atherogenesis. The role of TLR4 expression and regulation in LPS-stimulated VSMCs remains unclear. TLR4 mRNAs often contain AU-rich elements (AREs) in their 3' untranslated regions (3'UTR) which have a high affinity for RNA-binding proteins. It is not know whether the RNA-binding protein, human antigen R (HuR), regulates TLR4 expression in human aortic smooth muscle cells (HASMCs).

METHODS AND RESULTS

Stimulation of HASMCs with LPS significantly increased the cytosolic HuR level in vitro. Immunoprecipitation and RT-PCR demonstrated that LPS markedly increased the interaction of HuR and 3'UTR of TLR4 mRNA. The reporter plasmid, which contains the 3'UTR of TLR4 mRNA, significantly increased luciferase reporter gene expression in LPS-induced HASMCs. These data suggest that the 3'UTR of TLR4 mRNA confers LPS responsiveness and that HuR modulates 3'UTR-mediated gene expression. Knock-down of HuR inhibited LPS-induced TLR4 mRNA stability in HASMCs and luciferase reporter gene expression in CMV-Luciferase-TLR4 3'UTR-transfected HASMCs. In addition, inhibition of NADPH oxidase activity by diphenylene iodonium, knock-down of Rac1 gene expression by siRNA, and decrease of p38 MAPK activity by SB203580 significantly decreased the cytosolic HuR level, which mediates TLR4 mRNA stability.

CONCLUSIONS

Activation of NADPH oxidase and the MAPK-signaling pathway contribute to HuR-mediated stabilization of TLR4 mRNA induced by LPS in HASMCs. In the balloon injured rabbit aorta model, systemic inflammation induced by LPS caused intimal hyperplasia and increased TLR4 and HuR expression.

Potential therapeutic role for statins in respiratory disease

Statins reduce cholesterol levels by inhibiting 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and have an established role in the treatment of atherosclerotic disease. Recent research has identified anti-inflammatory properties of statins. Statins appear to reduce the stability of lipid raft formation with subsequent effects on immune activation and regulation, and also prevent the prenylation of signalling molecules with subsequent downregulation of gene expression. Both these effects result in reduced cytokine, chemokine, and adhesion molecule expression, with effects on cell apoptosis or proliferation. This review considers the evidence for the anti-inflammatory properties of statins in the lung, and how these effects are being applied to research into the role of statins as a novel treatment of respiratory diseases.

Statins and the endothelium

Statins have been shown to have pleiotropic effects apart from serum lipid-lowering effect in human. One of the major target organs for the effects of statins is the vascular endothelium, which plays an important role in the development of atherosclerosis and angiogenesis. Recent numerous studies have shown that the statins' cholesterol-independent vascular effects appear to involve directly restoring or improving endothelial function by increasing NO production, promoting re-endothelialization after arterial injury, and inhibiting inflammatory responses within the vessel wall that are thought to contribute to atherosclerosis. This review provides an update of the unique effects of statins on endothelial cells including endothelial progenitor cells as well as highlighting the therapeutic potential of statins beyond their established lipid-lowering effects.

Modulatory Effects of Atorvastatin on Endothelial Cell–Derived Chemokines, Cytokines, and Angiogenic Factors

STUDY OBJECTIVE

To investigate the immunomodulatory effects of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) by determining whether atorvastatin alters the production of specific endothelium-derived immunoactive proteins and whether its treatment effects depend on its concentration and/or inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase.

DESIGN

In vitro study using a multiplexing method for protein measurement.

SETTING

University laboratory.

MEASUREMENTS AND MAIN RESULTS

Human umbilical vein endothelial cells were cultured to approximately 80% confluence and treated with atorvastatin 1-50 microM alone or with mevalonate for 24 hours. Untreated cells served as controls. Culture-conditioned media were removed and multiplex assayed for protein content of epithelial neutrophil-activating peptide-78, interleukin-8, monocyte chemotactic protein-1, interleukin-6, interleukin-10, fibroblast growth factor, and granulocyte colony stimulating factor. Atorvastatin significantly reduced the production of epithelial neutrophil-activating peptide-78, interleukin-6, interleukin-8, and monocyte chemotactic protein-1 (p<0.001 to p<0.05) in a concentration-dependent manner without affecting basal production of interleukin-10, fibroblast growth factor, and granulocyte colony stimulating factor. The treatment effects of atorvastatin were reversed with concurrent mevalonate therapy.

CONCLUSION

By inhibiting 3-hydroxy-3-methylglutaryl coenzyme A reductase, atorvastatin lowered concentrations of several inflammatory molecules derived from basal-state endothelial cells in a concentration-dependent manner. The in vivo importance of these immunomodulatory effects needs further investigation.

Statin therapy is associated with fewer deaths in patients with bacteraemia

OBJECTIVE

Beneficial effects with statin use are increasingly reported in a variety of patient groups. There is in vitro and clinical evidence for its antiinflammatory and immunomodulatory therapeutic roles. We aimed to assess the association between statin administration and mortality in bacteraemic patients.

DESIGN

A retrospective cohort analysis.

SETTING

A 300-bed acute general hospital.

PATIENTS AND PARTICIPANTS

All patients (n=438) requiring hospital care for an episode of bacteraemia during the years 2000-2003 were included. Statin use, patient outcome, and clinical and laboratory variables were collected.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

There was a significant reduction in all-cause hospital mortality (10.6% vs. 23.1%, p=0.022) and death attributable to bacteraemia (6.1% vs. 18.3%, p=0.014) in patients who were receiving statin therapy at the time of bacteraemia (n=66). The reduction in all-cause hospital mortality (1.8% vs. 23.1%, p=0.0002) and death attributable to bacteraemia (1.8% vs. 18.3%, p=0.0018) was more pronounced in the patients who continued to receive statin therapy after the diagnosis of bacteraemia (n=56). The apparent mortality benefit persisted after controlling for differences between the groups. Statin use prior to admission was associated with a reduced adjusted hospital mortality rate (odds ratio 0.39; CI 95% 0.17, 0.91; p=0.029), and continuing statin use after bacteraemia increased this effect (odds ratio 0.06; CI 95% 0.01, 0.44; p=0.0056).

CONCLUSION

This retrospective study demonstrates a significant survival benefit associated with continuing statin therapy in bacteraemic patients. The potential for statins as an adjuvant therapy in sepsis warrants further investigation.

Characterization of the expression of TLR2 (toll-like receptor 2) and TLR4 on circulating monocytes in coronary artery disease

TLRs are receptors involved in the recognition of pathogens by the innate immune system, and TLR2 and TLR4 play important roles in the activation of monocytes. A total of 105 consecutive patients who underwent coronary angiography comprised of 46 with stable effort angina (SA), 41 with unstable angina (UA), and 18 with no significant CAD (CNT) were enrolled. The baseline expression levels of TLR2 and TLR4 on monocytes in peripheral blood mononuclear cells (PBMCs) were determined by flow-cytometric analysis. Since TLR2 expression has been reported to be regulated by TLR4 signaling, we cultured PBMCs with or without lipopolysaccharide (LPS, 1 microg/ml). At baseline, TLR4 levels (mean of fluorescence intensity ) in SA (145 +/- 58, p < 0.05) and UA (164 +/- 65, p < 0.01) were higher than those in CNT (107 +/- 37). As for TLR2, levels were higher in UA (108 +/- 36, p < 0.05) than in SA (94 +/- 18) and CNT (87 +/- 22). After stimulation with LPS, TLR2 levels increased in SA but decreased in UA. In conclusions, TLR4 levels increased in both SA and UA. Monocytes in UA were characterized by elevated TLR2 levels and unresponsiveness of the TLR2 levels to TLR4 stimulation.

Variation in the toll-like receptor 4 gene and susceptibility to myocardial infarction

Variation in the gene encoding toll-like receptor 4 (TLR4), a transmembrane receptor that mediates inflammatory responses to bacterial endotoxin, has been associated with susceptibility to atherosclerosis and its complications, such as myocardial infarction (MI), the pathogenesis of which involves inflammation. A recent study has also indicated that TLR4 gene variation influences the effect of statin treatment on reducing atherosclerosis complications. We studied the TLR4 gene Asp299Gly polymorphism in relation to susceptibility to myocardial infarction in a cohort of patients with angiographically documented coronary artery disease, and performed a meta-analysis using data sets from three independent studies. The meta-analysis showed that overall, odds ratio (OR) for MI was 0.73 [95% confidence interval (CI) 0.55-0.96, P=0.024] in 299Gly carriers compared to non-carriers, and there was no evidence of heterogeneity among the sample sets (P=0.679). In our patient cohort, a significant association of 299Gly bearing genotypes with lower susceptibility to myocardial infarction was observed only in patients receiving statin treatment, with 299Gly carriers having an OR of 0.49 (95% CI 0.27-0.78, P=0.015) for MI compared to non-carriers. These results are consistent with the notion that variation in the TLR4 gene contributes to inter-individual variability in susceptibility to coronary ischaemic events, and that TLR4 genotype and statin treatment may have a synergistic effect.

Lipopolysaccharide-Induced Cytokine and Chemokine Expression in Human Carotid Lesions

The release of cytokines and chemokines from activated immune-competent cells plays a crucial role in determining the pathology of the atherogenic progress. We investigated the effect of bacterial lipopolysaccharide (LPS) on cytokine/chemokine expression in carotid lesions and normal renal arteries. The lesions or renal arteries were incubated for 6 h at 37 degrees C in serum-free media treated with or without LPS. After LPS treatment, increased protein levels of IL-1beta, IL-6, IL-8, IL-10, TNF-alpha and MCP-1 were observed in the culture medium from the lesions measured with cytometric bead array. We were able to detect the induction of IL-1beta, IL-6, IL-8, IL-10, TNF-alpha and MCP-1 mRNA in the lesions after stimulation with LPS using real-time PCR. In renal arteries, LPS also induces mRNA expression of all chemokines and cytokines investigated with the exception of IL-6. However, LPS induces significantly higher levels of TNF-alpha, IL-1beta and IL-10 mRNA in lesions compared to renal arteries. The results suggest that infectious agents are capable of enhancing the production of cytokines/chemokines in an already ongoing inflammatory process such as in atherosclerosis, and that low levels of circulating LPS may affect the levels of pro-inflammatory cytokines much more in atherosclerotic vessels than in normal vessels and may contribute to the development of the atherosclerotic lesion.

Hydroxymethylglutaryl co-enzyme A reductase inhibition attenuates endotoxin-mediated inflammatory responses

Background

The aim of this study was to investigate whether inhibition of hydroxymethylglutaryl co-enzyme A reductase attenuates leucocyte–endothelial cell interactions and alters expression of endothelial constitutive nitric oxide synthase (ecNOS) and inducible nitric oxide synthase (iNOS) following exposure to endotoxin.

Methods

Male Sprague–Dawley rats were randomized into control, lipopolysaccharide (LPS) and pravastatin + LPS groups (seven per group). Pravastatin sodium was gavaged at 0·4 mg per kg per day for 5 days, after which LPS 15 mg/kg was administered via the jugular vein. Intravital microscopy was used to determine leucocyte–endothelial cell interactions.

Results

Following the administration of LPS there was a significant reduction in leucocyte rolling velocity at 10 min (mean(s.e.m.) 69(3) versus 102(6) per cent of baseline value; P = 0·041), an increase in the number of adherent leucocytes at 10 min (4·5(0·5) versus 2·8(0·3) per 100 µm; P = 0·044) and an increase in the number of leucocytes undergoing transendothelial migration at 30 min (4·2(0·4) versus 1·7(0·4) per field; P = 0·008) compared with controls. Pretreatment with pravastatin significantly attenuated LPS-induced leucocyte–endothelial cell interactions (rolling velocity 89(6) per cent at 10 min, P = 0·038; adherent leucocytes 3·0(0·5) per 100 µm at 10 min, P = 0·038; migrating leucocytes 1·9(0·5) per field at 30 min, P = 0·001). This endothelial protection was associated with maintenance of ecNOS and reduced iNOS expression within mesenteric tissues.

Conclusion

These data show that pravastatin produces anti-inflammatory effects in response to injurious stimuli by attenuation of leucocyte–endothelial cell interactions.

Oxidized omega-3 fatty acids inhibit pro-inflammatory responses in glomerular endothelial cells

BACKGROUND

Omega-3 fatty acids have beneficial effects in chronic inflammatory diseases that are characterized by accumulation of leukocytes and leukocyte-mediated tissue injury. Accumulation of leukocytes occurs, in part, due to pro-inflammatory responses in endothelial cells, such as increase in expression of leukocyte adhesion receptors and chemokines, such as MCP-1 and IL-8.

METHODS

omega-3 fatty acids, such as EPA, are highly polyunsaturated and readily undergo auto-oxidation. We studied the effect of oxidized EPA and unoxidized (native) EPA on leukocyte-glomerular endothelial cell interactions using adhesion assays, ELISA assays and transmigration assays. We used electrophoresis mobility shift assays to determine the effect of oxidized and unoxidized EPA on cytokine-induced nuclear factor-kappaB (NF-kappaB) activation.

RESULTS

Oxidized EPA but not unoxidized EPA dose-dependently inhibits cytokine-induced leukocyte adhesion receptors on glomerular endothelial cells, which correlates with inhibition of leukocyte-glomerular endothelial cell interactions. Oxidized EPA but not unoxidized EPA inhibits cytokine-induced glomerular endothelial and mesangial cell expression of MCP-1, and to a lesser extent IL-8. Transmigration assays show that oxidized EPA but not unoxidized EPA inhibits leukocyte transmigration across glomerular endothelial cells. Oxidized EPA but not unoxidized EPA potently inhibited cytokine-induced activation of NF-kappaB in glomerular endothelial and mesangial cells.

CONCLUSIONS

These studies show that the beneficial effects of fish oil in chronic inflammatory diseases, including IgA nephropathy, may result from the inhibitory effects of oxidized omega-3 fatty acids on pro-inflammatory events in endothelial cells via inhibition of NF-kappaB activation.

Statins decrease Toll-like receptor 4 expression and downstream signaling in human CD14+ monocytes

OBJECTIVE

Anti-inflammatory effects of statins contribute to their clinical benefit. Molecular mechanisms underlying these effects have not been well explored. Because statins attenuate lipopolysaccharide (LPS) responsiveness, we hypothesized that part of the pleiotropic effects are mediated through innate immunity.

METHODS AND RESULTS

Toll-like receptor (TLR) 4 expression and downstream signaling in CD14+ monocytes after incubation with simvastatin and atorvastatin were quantified via flow-cytometry, quantitative RT-PCR, kinase assay, and enzyme-linked immunosorbent assay. Incubation with intermediates/ inhibitors of the mevalonate pathway was used to identify the mode of statin action. Statin incubation resulted in a dose-dependent reduction of TLR4 expression (53+/-7.6% reduction compared with untreated monocytes; P<0.005), transcript levels (68+/-6.3%; P<0.002), decreased IRAK phosphorylation (37+/-8.3%; P<0.05), and LPS-induced IL-6, IL-12, tumor necrosis factor (TNF)-alpha, and B7-1 expression (P<0.05). Four weeks of treatment with atorvastatin significantly reduced TLR4 expression on circulating CD14+ monocytes by 36.2+/-4.2% (P<0.05). Effects of statins were reversed by mevalonate (P=0.57). Incubation with specific inhibitors of geranylgeranyltransferase (54+/-4.3%), farnesyltransferase (57+/-5.1%), or with clostridium-difficile toxin B (58+/-6.1%, P<0.01) imitated the statin effects. Whereas wortmannin and LY294002 inhibited the statin effect (P=0.27), incubation with a specific RhoA kinase inhibitor had no effect (P=0.57).

CONCLUSIONS

Statins influence TLR4 expression and signaling via inhibition of protein geranylgeranylation and farnesylation. These observations imply interactions with innate immunity as one pleiotropic mechanism.

Effects of Porphyromonas gingivalis antigens and proinflammatory cytokines on human coronary artery endothelial cells

OBJECTIVE

Individuals with periodontitis have been cited as having a significantly increased risk of developing coronary heart disease. Although accumulating evidence suggests that periodontal infection is involved in the development and progression of atherosclerosis, the underlying mechanisms remain to be elucidated. In the present study, we examined how periodontal infection could contribute to endothelial dysfunction.

METHODS

Human coronary arterial endothelial cells were stimulated with tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta, both of which are reported to be elevated in the serum of periodontitis patients. Cells were also stimulated with lipopolysaccharide, outer membrane protein and heat shock protein 60 derived from Porphyromonas gingivalis, a representative periodontopathic bacterium which is known to stimulate myeloid cells.

RESULTS

Although TNF-alpha and IL-1beta, at concentrations a little higher than those in sera of periodontitis patients, up-regulated the expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, P. gingivalis antigens had only a slight stimulatory effect.

CONCLUSION

Experiments in which the total pathogen burden is considered, rather than a single species of bacteria, would increase our understanding of the contribution of which periodontal infection to atherogenesis.

Effect of Monthly Atorvastatin and Fenofibrate Treatment on Monocyte Chemoattractant Protein-1 Release in Patients with Primary Mixed Dyslipidemia

The aim of this study was to compare the effect of 30-day treatment with atorvastatin and fenofibrate on monocyte release and plasma levels of monocyte chemoattractant protein-1 (MCP-1). We studied 52 atherosclerotic patients with primary mixed dyslipidemia and 16 age-, sex-, and weight-matched control subjects with asymptomatic atherosclerosis. Dyslipidemic patients enrolled into the study were randomly divided into three groups, simultaneously treated with atorvastatin (20 mg/d, n = 18), fenofibrate (267 mg/d, n = 16), or placebo (n = 18). Plasma lipid-profile and content of MCP-1, and monocyte release of this chemokine were measured at baseline and after 30 days of therapy. Compared with the control subjects, dyslipidemic patients exhibited the increased plasma levels and monocyte MCP-1 release. Atorvastatin and fenofibrate not only improved lipid profile but also decreased monocyte secretion of this chemokine. Moreover, hypolipemic agents slightly reduced its plasma levels. MCP-1-lowering effect of atorvastatin and fenofibrate did not correlate with the lipid-lowering potential of these agents. Our results suggest that atorvastatin and fenofibrate produce their antiinflammatory effect partially via inhibiting monocyte release of MCP-1. The treatment-induced reduction in its secretion may contribute to the clinical effectiveness of statins and fibrates in the therapy for atherosclerosis and other chronic fibroproliferative diseases.

Potential Role of Endotoxin as a Proinflammatory Mediator of Atherosclerosis

Atherosclerosis is increasingly recognized as a chronic inflammatory disease. Although a variety of inflammatory markers (ie, C-reactive protein) have been associated with atherosclerosis and its consequences, it is important to identify principal mediators of the inflammatory responses. One potentially important source of vascular inflammation in atherosclerosis is bacterial endotoxin. Mutations in Toll-like receptor 4 (TLR-4), an integral component of the endotoxin signaling complex, are fairly common in the Caucasian population and have recently been associated with reduced incidence of atherosclerosis and other cardiovascular diseases in some studies. Moreover, epidemiological studies suggest that endotoxemia at levels as low as 50 pg/mL constitutes a strong risk factor for the development of atherosclerosis. Endotoxin concentrations in this range may be produced by a variety of common subclinical Gram-negative infections. In this article, we outline the main elements of the endotoxin signaling receptor complex that initiates proinflammatory signaling (lipopolysaccharide binding protein [LBP], CD14, TLR-4, and MD-2) and discuss how changes in expression of these molecules may affect proatherogenic responses in the vessel wall. We also describe some of the proinflammatory effects of endotoxin that may be relevant to atherosclerosis, and discuss how serum lipoproteins, especially high-density lipoprotein, may modulate endotoxin-induced inflammatory responses. Further, we discuss recent findings suggesting that the lipid-lowering statins may have an additional protective role in blocking at least some of these proinflammatory signaling pathways. Finally, we discuss species diversity with regard to endotoxin signaling that should be considered when extrapolating experimental data from animal models to humans.

Arterial endothelial injury due to infection in childhood: ticking bomb or innocent bystander?

Atherosclerosis is regarded as a chronic disease that begins in early life. While the main underlying mechanism of atherosclerosis is nowadays unequivocally attributed to a low-grade inflammatory reaction, the spectrum of aetiological conditions is far from being fully elucidated. Both viruses and bacteria have been suggested to intervene at various stages of atherosclerosis development, although a clear pathogenic link between infection and atherosclerosis remains debatable. As one key event in atherogenesis involves a perturbation of the protective mechanisms normally posed by the arterial endothelium, a number of studies have enquired into the possible detrimental effects of microbes and their components on the endothelial cells. This review aims to scrutinize the current literature in this regard, and to suggest several possible directions for future studies.

Regulation of endotoxin-induced proinflammatory activation in human coronary artery cells: expression of functional membrane-bound CD14 by human coronary artery smooth muscle cells

Low-level endotoxemia has been identified as a powerful risk factor for atherosclerosis. However, little is known about the mechanisms that regulate endotoxin responsiveness in vascular cells. We conducted experiments to compare the relative responses of human coronary artery endothelial cells (HCAEC) and smooth muscle cells (HCASMC) to very low levels of endotoxin, and to elucidate the mechanisms that regulate endotoxin responsiveness in vascular cells. Endotoxin (</=1 ng/ml) caused production of chemotactic cytokines in HCAEC. Endotoxin-induced cytokine production was maximal at LPS-binding protein:soluble CD14 ratios <1, typically observed in individuals with subclinical infection; higher LPS-binding protein:soluble CD14 ratios were inhibitory. Endotoxin potently activated HCASMC, with cytokine release >10-fold higher in magnitude at >10-fold lower threshold concentrations (10-30 pg/ml) compared with HCAEC. This remarkable sensitivity of HCASMC to very low endotoxin concentrations, comparable to that found in circulating monocytes, was not due to differential expression of TLR4, which was detected in HCAEC, HCASMC, and intact coronary arteries. Surprisingly, membrane-bound CD14 was detected in seven different lines of HCASMC, conferring responsiveness to endotoxin and to lipoteichoic acid, a product of Gram-positive bacteria, in these cells. These results suggest that the low levels of endotoxin associated with increased risk for atherosclerosis are sufficient to produce inflammatory responses in coronary artery cells. Because CD14 recognizes a diverse array of inflammatory mediators and functions as a pattern recognition molecule in inflammatory cells, expression of membrane-bound CD14 in HCASMC implies a potentially broader role for these cells in transducing innate immune responses in the vasculature.

Effect of soluble epoxide hydrolase inhibition on epoxyeicosatrienoic acid metabolism in human blood vessels

We investigated the effects of soluble epoxide hydrolase (sEH) inhibition on epoxyeicosatrienoic acid (EET) metabolism in intact human blood vessels, including the human saphenous vein (HSV), coronary artery (HCA), and aorta (HA). When HSV segments were perfused with 2 micromol/l 14,15-[3H]EET for 4 h, >60% of radioactivity in the perfusion medium was converted to 14,15-dihydroxyeicosatrienoic acid (DHET). Similar results were obtained with endothelium-denuded vessels. 14,15-DHET was released from both the luminal and adventitial surfaces of the HSV. When HSVs were incubated with 14,15-[3H]EET under static (no flow) conditions, formation of 14,15-DHET was detected within 15 min and was inhibited by the selective sEH inhibitors N,N'-dicyclohexyl urea and N-cyclohexyl-N'-dodecanoic acid urea (CUDA). Similarly, CUDA inhibited the conversion of 11,12-[3H]EET to 11,12-DHET by the HSV. sEH inhibition enhanced the uptake of 14,15-[3H]EET and facilitated the formation of 10,11-epoxy-16:2, a beta-oxidation product. The HCA and HA converted 14,15-[3H]EET to DHET, and this also was inhibited by CUDA. These findings in intact human blood vessels indicate that conversion to DHET is the predominant pathway for 11,12- and 14,15-EET metabolism and that sEH inhibition can modulate EET metabolism in vascular tissue.

Oxidized omega-3 fatty acids inhibit NF-kappaB activation via a PPARalpha-dependent pathway

OBJECTIVE

The aim of this study was to determine the effects of oxidized versus native omega-3 fatty acids on the endothelial expression of chemokines MCP-1 and IL-8, and, if effective in inhibiting chemokine expression, to determine the mechanism for the inhibition of chemokine expression.

METHODS AND RESULTS

Using enzyme-linked immunosorbent assays, we show that oxidized EPA and DHA but not unoxidized EPA or DHA inhibit cytokine-induced endothelial expression of monocyte chemoattractant protein (MCP)-1 and, to a lesser extent, IL-8. In electrophoretic mobility shift assays, oxidized EPA but not unoxidized EPA potently inhibited cytokine-induced activation of endothelial nuclear factor-kappaB (NF-kappaB). Using Western blot analyses, we show that the inhibition of NF-kappaB activation was not caused by prevention of phosphorylation of IkappaBalpha because oxidized EPA did not inhibit cytokine-induced phosphorylation and ubiquination of IkappaBalpha. Furthermore, oxidized EPA inhibited NF-kappaB activation in endothelial cells derived from wild-type mice but had no inhibitory effects on NF-kappaB activation in endothelial cells derived from peroxisome proliferator-activated receptor alpha (PPARalpha)-deficient mice, indicating that oxidized EPA requires PPARalpha for its inhibitory effects on NF-kappaB.

CONCLUSIONS

These studies show that the antiinflammatory effects of fish oil may result from the inhibitory effects of oxidized omega-3 fatty acids on NF-kappaB activation via a PPARalpha-dependent pathway.

Involvement of periodontopathic biofilm in vascular diseases

Oral bacteria inhabit biofilms, which are firm clusters adhering in layers to surfaces and are not easily eliminated by immune responses and are resistant to antimicrobial agents. Dental plaque is one such biofilm. In the past 10 years, subgingival plaque bacteria forming biofilms have been increasingly reported to be involved in systemic diseases. A close relationship between microbial infections and vascular disease has also been reported in the past two decades. The present review discusses the significance of the ecologic characteristics of biofilms formed by periodontopathic bacteria in order to further clarify the associations between periodontal disease and systemic disease. We focus on the relationships between periodontal disease-associated bacteria forming biofilms and vascular diseases including atherosclerosis and carotid coronary stenotic artery disease, and we discuss the direct and indirect effects on vascular diseases of lipopolysaccharides as well as heat shock proteins produced by periodontopathic bacteria.