Very low density lipoprotein potentiates tumor necrosis factor-α expression in macrophages

Secondary rotational atherectomy is associated with reduced occurrence of prolonged ST-segment elevation following ablation

Elevation of the ST segment after percutaneous coronary intervention (PCI) using rotational atherectomy (RA) for severely calcified lesions often persists after disappearance of the slow-flow phenomenon on angiography. We investigated clinical factors relevant to prolonged ST-segment elevation following RA among 152 patients with stable angina undergoing elective PCI. PCI procedures were divided into two strategies, RA without (primary RA strategy) or with (secondary RA strategy) balloon dilatation before RA. Incidence of prolonged ST-segment elevation after disappearance of slow-flow phenomenon was higher in the 56 patients with primary RA strategy (13%) than in the 96 patients with secondary RA strategy (3%, p = 0.039). Univariate logistic regression analysis showed levels of low-density lipoprotein cholesterol (LDL-C) (odds ratio [OR] 0.95, 95% confidence interval [CI] 0.93-0.99; p = 0.013), levels of triglycerides (OR 0.97, 95%CI 0.94-0.99; p = 0.040), and secondary RA strategy (OR 0.23, 95% CI 0.05-0.85; p = 0.028) were inversely associated with occurrence of prolonged ST-segment elevation following ablation. However, hemodialysis, diabetes mellitus, left-ventricular ejection fraction, lesion length ≥ 20 mm, and burr size did not show significant associations. Multivariate logistic regression analysis modeling revealed that secondary RA strategy was significantly associated with the occurrence of prolonged ST-segment elevation (Model 1: OR 0.24, 95% CI 0.05-0.95, p = 0.042; Model 2: OR 0.17, 95% CI 0.03-0.68, p = 0.018; Model 3: OR 0.21, 95% CI 0.03-0.87, p = 0.041) even after adjusting for levels of LDL-C and triglycerides. Secondary RA strategy may be useful to reduce the occurrence of prolonged ST-segment elevation following RA.

Disturbed lipid profile in common variable immunodeficiency - a pathogenic loop of inflammation and metabolic disturbances

The relationship between metabolic and inflammatory pathways play a pathogenic role in various cardiometabolic disorders and is potentially also involved in the pathogenesis of other disorders such as cancer, autoimmunity and infectious diseases. Common variable immunodeficiency (CVID) is the most common primary immunodeficiency in adults, characterized by increased frequency of airway infections with capsulated bacteria. In addition, a large proportion of CVID patients have autoimmune and inflammatory complications associated with systemic inflammation. We summarize the evidence that support a role of a bidirectional pathogenic interaction between inflammation and metabolic disturbances in CVID. This include low levels and function of high-density lipoprotein (HDL), high levels of triglycerides (TG) and its major lipoprotein very low-density lipoprotein (VLDL), and an unfavorable fatty acid (FA) profile. The dysregulation of TG, VLDL and FA were linked to disturbed gut microbiota profile, and TG and VLDL levels were strongly associated with lipopolysaccharides (LPS), a marker of gut leakage in blood. Of note, the disturbed lipid profile in CVID did not include total cholesterol levels or high low-density lipoprotein levels. Furthermore, increased VLDL and TG levels in blood were not associated with diet, high body mass index and liver steatosis, suggesting a different phenotype than in patients with traditional cardiovascular risk such as metabolic syndrome. We hypothesize that these metabolic disturbances are linked to inflammation in a bidirectional manner with disturbed gut microbiota as a potential contributing factor.

Triglyceride and Triglyceride-Rich Lipoproteins in Atherosclerosis

Cardiovascular disease (CVD) is still the leading cause of death globally, and atherosclerosis is the main pathological basis of CVDs. Low-density lipoprotein cholesterol (LDL-C) is a strong causal factor of atherosclerosis. However, the first-line lipid-lowering drugs, statins, only reduce approximately 30% of the CVD risk. Of note, atherosclerotic CVD (ASCVD) cannot be eliminated in a great number of patients even their LDL-C levels meet the recommended clinical goals. Previously, whether the elevated plasma level of triglyceride is causally associated with ASCVD has been controversial. Recent genetic and epidemiological studies have demonstrated that triglyceride and triglyceride-rich lipoprotein (TGRL) are the main causal risk factors of the residual ASCVD. TGRLs and their metabolites can promote atherosclerosis via modulating inflammation, oxidative stress, and formation of foam cells. In this article, we will make a short review of TG and TGRL metabolism, display evidence of association between TG and ASCVD, summarize the atherogenic factors of TGRLs and their metabolites, and discuss the current findings and advances in TG-lowering therapies. This review provides information useful for the researchers in the field of CVD as well as for pharmacologists and clinicians.

New insight into dyslipidemia‐induced cellular senescence in atherosclerosis

Atherosclerosis, characterized by lipid‐rich plaques in the arterial wall, is an age‐related disorder and a leading cause of mortality worldwide. However, the specific mechanisms remain complex. Recently, emerging evidence has demonstrated that senescence of various types of cells, such as endothelial cells (ECs), vascular smooth muscle cells (VSMCs), macrophages, endothelial progenitor cells (EPCs), and adipose‐derived mesenchymal stem cells (AMSCs) contributes to atherosclerosis. Cellular senescence and atherosclerosis share various causative stimuli, in which dyslipidemia has attracted much attention. Dyslipidemia, mainly referred to elevated plasma levels of atherogenic lipids or lipoproteins, or functional impairment of anti‐atherogenic lipids or lipoproteins, plays a pivotal role both in cellular senescence and atherosclerosis. In this review, we summarize the current evidence for dyslipidemia‐induced cellular senescence during atherosclerosis, with a focus on low‐density lipoprotein (LDL) and its modifications, hydrolysate of triglyceride‐rich lipoproteins (TRLs), and high‐density lipoprotein (HDL), respectively. Furthermore, we describe the underlying mechanisms linking dyslipidemia‐induced cellular senescence and atherosclerosis. Finally, we discuss the senescence‐related therapeutic strategies for atherosclerosis, with special attention given to the anti‐atherosclerotic effects of promising geroprotectors as well as anti‐senescence effects of current lipid‐lowering drugs.

VLDL and HDL attenuate endoplasmic reticulum and metabolic stress in HL-1 cardiomyocytes

Lipoproteins have a vital role in the development of metabolic and cardiovascular diseases ranging from protective to deleterious effects on target tissues. VLDL has been shown to induce lipotoxic lipid accumulation and exert a variety of negative effects on cardiomyocytes. Lipotoxicity and endoplasmic reticulum (ER) stress are proposed to be the mediators of damaging effects of metabolic diseases on cardiovascular system. We treated cardiomyocytes with lipoproteins to evaluate the adaptability of these cells to metabolic stress induced by starvation and excess of lipoproteins, and to evaluate the effect of lipoproteins and lipid accumulation on ER stress. VLDL reversed metabolic stress induced by starvation, while HDL did not. VLDL induced dose-dependent lipid accumulation in cardiomyocytes, which however did not result in reduced cell viability or induction of ER stress. Moreover, VLDL or HDL pre-treatment reduced ER stress in cardiomyocytes induced by tunicamycin and palmitic acid as measured by the expression of ER stress markers, even in conditions of increased lipid accumulation. VLDL and HDL induced activation of pro-survival ERK1/2 in cardiomyocytes; however, this activation was not involved in the protection against ER stress. Additionally, we observed that LDLR and VLDLR are regulated differently by lipoproteins and cellular stress, as lipoproteins induced VLDLR protein independently of the level of lipid accumulation. We conclude that VLDL is not a priori detrimental for cardiomyocytes and can even have beneficial effects, enabling cell survival under starvation and attenuating ER stress.

Impact of Adrenal Steroids on Regulation of Adipose Tissue

Corticosteroids are secreted by the adrenal glands and control the functions of adipose tissue via the activation of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR). In turn, adipocytes release a large variety of adipokines into the bloodstream, regulating the function of several organs and tissues, including the adrenal glands, hereby controlling corticosteroid production. In adipose tissue, the activation of the MR by glucocorticoids (GC) and aldosterone affects important processes such as adipocyte differentiation, oxidative stress, autophagic flux, adipokine expression as well as local production of GC through upregulation of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Notably, the proinflammatory responses induced by the MR are counteracted by activation of the GR, whose activity inhibits the expression of inflammatory adipokines. Both GR and MR are deeply involved in adipogenesis and adipose expansion; hence pharmacological blockade of these two receptors has proven effective against adipose tissue dysfunction in experimental models of obesity and metabolic syndrome (MetS), suggesting a potential use for MR and GR antagonists in these clinical settings. Importantly, obesity and Cushing's syndrome (CS) share metabolic similarities and are characterized by high levels of circulating corticosteroids, which in turn are able to deeply affect adipose tissue. In addition, pharmacological approaches aimed at reducing aldosterone and GC levels, by means of the inhibition of CYP11B2 (aldosterone synthase) or 11β-HSD1, represent alternative strategies to counter the detrimental effects of excessive levels of corticosteroids, which are often observed in obesity and, more general, in MetS. © 2017 American Physiological Society. Compr Physiol 7:1425-1447, 2017.

Quercetin prevents left ventricular hypertrophy in the Apo E knockout mouse

Hypercholesterolemia is a risk factor for the development of hypertrophic cardiomyopathy. Nevertheless, there are few studies aimed at determining the effects of dietary compounds on early or mild cardiac hypertrophy associated with dyslipidemia. Here we describe left ventricular (LV) hypertrophy in 12 week-old Apo E^−/− hypercholesterolemic mice. The LV end diastolic posterior wall thickness and overall LV mass were significantly increased in Apo E^−/− mice compared with wild type (WT) controls. Fractional shortening, LV end diastolic diameter, and hemodynamic parameters were unchanged from WT mice. Oral low dose quercetin (QCN; 0.1 µmol QCN/kg body weight for 6 weeks) significantly reduced total cholesterol and very low density lipoprotein in the plasma of Apo E^−/− mice. QCN treatment also significantly decreased LV posterior wall thickness and LV mass in Apo E^−/− mice. Myocardial geometry and function were unaffected in WT mice by QCN treatment. These data suggest that dietary polyphenolic compounds such as QCN may be effective modulators of plasma cholesterol and could prevent maladaptive myocardial remodeling.

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Oral low doses of Quercetin resulted in peak plasma levels of approximately 100 nM.

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Quercetin had no effect on cholesterol profiles in wild type mice but decreased VLDL in ApoE^−/− mice.

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Quercetin treatment attenuated the cardiac hypertrophy in ApoE^−/− mice but had no effects on heart function in wild type mice.

Very low density lipoproteins derived from periodontitis patients facilitate macrophage activation via lipopolysaccharide function

OBJECTIVE

Periodontitis, a chronic oral infection caused mainly by gram-negative bacteria, induces endotoxemia and associates with the risk for atherosclerosis. We investigated the effect of periodontal treatment on proatherogenic properties of very low density lipoproteins (VLDL).

METHODS

VLDL were isolated from 30 systemically healthy periodontitis patients before (pre-treatment) and 3 months after treatment (post-treatment). The mass compositions were analyzed, and VLDL-induced changes in cellular cholesterol content and expression of selected genes of human THP-1 macrophages were measured.

RESULTS

Periodontal treatment decreased the local inflammation in the periodontium, but did not have a significant effect on C-reactive protein (CRP) levels, VLDL composition, or VLDL potential to induce cholesterol uptake or gene expression by the macrophages. Incubation of macrophages in the presence of VLDL resulted in more than twofold increase in their cellular cholesterol content. Uptake of VLDL with ensuing macrophage cholesterol accumulation correlated positively with VLDL-associated lipopolysaccharide (LPS) activity (r=0.436, P=.016) and apolipoprotein E content (r=0.374, P=.046). Pre-treatment VLDL derived from the patients with high CRP levels displayed higher LPS activity than that of VLDL derived from patients with low CRP (above vs. below median, P=.007). In addition, pre-treatment VLDL isolated from patients with high systemic inflammation induced higher relative mRNA expression of CD14, TNF-α, MCP-1, and IL-6 in the macrophages.

CONCLUSION

Inflammation and endotoxemia induced by severe periodontitis may increase VLDL-dependent macrophage activation and cellular cholesterol accumulation, and thereby atherogenesis.

Triglyceride accumulation in macrophages upregulates paraoxonase 2 (PON2) expression via ROS-mediated JNK/c-Jun signaling pathway activation

The aim of this study was to analyze the effect and mechanism of action of macrophage triglyceride accumulation on cellular PON2 expression. Incubation of J774A.1 (murine macrophages) with VLDL (0-75 μg protein/mL) significantly and dose-dependently increased cellular triglyceride mass, and reactive oxygen species (ROS) formation, by up to 3.3- or 1.8-fold, respectively. PON2 expression (mRNA, protein, activity) in cells treated with VLDL (50 μg protein/mL) was higher by 2- to 3-fold, as compared with control cells. Similar effects were noted upon using THP-1 (human macrophages). Incubation of macrophages with synthetic triglyceride or triglyceride fraction from carotid lesion resulted in similar effects, as shown for VLDL. Upon using specific inhibitors of MEK1/2 (UO126, 10 μM), p38 (SB203580, 10 μM), or JNK (SP600125, 20 μM), we demonstrated that MEK, as well as JNK, but not p38, are involved in VLDL-induced macrophage PON2 upregulation. VLDL activated JNK (but not ERK), which resulted in c-Jun phosphorylation. This signaling pathway is probably activated by ROS, since the antioxidant reduced glutathione (GSH), significantly decreased VLDL-induced macrophage ROS formation, c-Jun phosphorylation and PON2 overexpression. We conclude that macrophage triglyceride accumulation upregulates PON2 expression via MEK/ JNK/c-Jun pathway, and these effects could be related, at least in part, to cellular triglycerides-induced ROS formation. ©

Activation of peroxisome proliferator-activated receptor δ inhibits human macrophage foam cell formation and the inflammatory response induced by very low-density lipoprotein

OBJECTIVE

Hypertriglyceridemia is an important risk factor for cardiovascular disease. Elevated plasma very low-density lipoprotein (VLDL) puts insulin-resistant patients at risk for atherosclerosis. VLDL readily induces macrophage lipid accumulation and inflammatory responses, for which targeted therapeutic strategies remain elusive. We examined the ability of VLDL to induce macrophage foam cells and the inflammatory response and sought to define the cell signaling cascades involved. We further examined the potential of peroxisome proliferator-activated receptor (PPAR) δ activation to attenuate both VLDL-stimulated lipid accumulation and cytokine expression.

METHODS AND RESULTS

THP-1 macrophages exposed to VLDL displayed significant triglyceride accumulation, which was attenuated by PPARδ activation. PPARδ agonists stimulated a transcriptional program resulting in inhibition of lipoprotein lipase activity, activation of fatty acid uptake, and enhanced β-oxidation. VLDL-treated macrophages significantly increased the expression of activator protein 1 associated cytokines interleukin-1β, macrophage inflammatory protein 1α, and intercellular adhesion molecule-1. VLDL treatment significantly increased the phosphorylation of both extracellular signal-related kinase 1 and 2 and p38. VLDL reduced AKT phosphorylation as well as its downstream effector forkhead box protein O1, concomitant with increased nuclear forkhead box protein O1. Cells treated with PPARδ agonists were completely resistant to VLDL-induced expression of inflammatory cytokines, mediated by normalization of mitogen-activated protein kinase (MAPK)(erk) and AKT/forkhead box protein O1 signaling.

CONCLUSIONS

The combined PPARδ-mediated reductions of lipid accumulation and inflammatory cytokine expression suggest a novel macrophage-targeted therapeutic option in treating atherosclerosis.

Human native lipoprotein-induced de novo DNA methylation is associated with repression of inflammatory genes in THP-1 macrophages

Background

We previously showed that a VLDL- and LDL-rich mix of human native lipoproteins induces a set of repressive epigenetic marks, i.e. de novo DNA methylation, histone 4 hypoacetylation and histone 4 lysine 20 (H4K20) hypermethylation in THP-1 macrophages. Here, we: 1) ask what gene expression changes accompany these epigenetic responses; 2) test the involvement of candidate factors mediating the latter. We exploited genome expression arrays to identify target genes for lipoprotein-induced silencing, in addition to RNAi and expression studies to test the involvement of candidate mediating factors. The study was conducted in human THP-1 macrophages.

Results

Native lipoprotein-induced de novo DNA methylation was associated with a general repression of various critical genes for macrophage function, including pro-inflammatory genes. Lipoproteins showed differential effects on epigenetic marks, as de novo DNA methylation was induced by VLDL and to a lesser extent by LDL, but not by HDL, and VLDL induced H4K20 hypermethylation, while HDL caused H4 deacetylation. The analysis of candidate factors mediating VLDL-induced DNA hypermethylation revealed that this response was: 1) surprisingly, mediated exclusively by the canonical maintenance DNA methyltransferase DNMT1, and 2) independent of the Dicer/micro-RNA pathway.

Conclusions

Our work provides novel insights into epigenetic gene regulation by native lipoproteins. Furthermore, we provide an example of DNMT1 acting as a de novo DNA methyltransferase independently of canonical de novo enzymes, and show proof of principle that de novo DNA methylation can occur independently of a functional Dicer/micro-RNA pathway in mammals.

Proteomic analysis of the triglyceride-rich lipoprotein-laden foam cells

In hypertriglyceridaemic individuals, atherosclerogenesis is associated with the increased concentrations of very low density lipoprotein (VLDL) and VLDL-associated remnant particles. In vitro studies have suggested that VLDL induces foam cells formation. To reveal the changes of the proteins expression in the process of foam cells formation induced by VLDL, we performed a proteomic analysis of the foam cells based on the stimulation of differentiated THP-1 cells with VLDL. Using two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, 14 differentially expressed proteins, containing 8 up-regulated proteins and 6 down-regulated proteins were identified. The proteins are involved in energy metabolism, oxidative stress, cell growth, differentiation and apoptosis, such as adipose differentiation-related protein (ADRP), enolase, S100A11, heat shock protein 27 and so on. In addition, the expression of some selected proteins was confirmed by Western blot and RT-PCR analysis. The results suggest that VLDL not only induces lipid accumulation, but also brings about foam cells diverse characteristics by altering the expression of various proteins.

Lipopolysaccharide associates with pro-atherogenic lipoproteins in periodontitis patients

INTRODUCTION

Periodontitis patients are known to suffer from endotoxemia, which may be among the major risk factors for atherosclerosis. In health, lipopolysaccharide (LPS) is mainly carried with high density lipoprotein (HDL) particles. Shift of LPS toward lipoproteins with lower densities may result in less effective endotoxin scavenging. Our aim was to determine plasma LPS activity and lipoprotein-distribution before and after treatment in periodontitis patients.

PATIENTS AND METHODS

Very low and intermediate density (VLDL-IDL), low density (LDL), HDL 2, HDL3, and lipoprotein-deficient plasma (LPDP) were isolated by sequential ultracentrifugation. Patients included 34 subjects aged 53.5 +/- 8.3 years, before and 6 months after periodontal treatment.

RESULTS

The mean LPS distribution decreased among lipoprotein classes as follows: VLDL-IDL 41.3 +/- 12.1%, LPDP 25.0 +/- 7.0%, HDL3 13.1 +/- 5.2%, LDL 11.5 +/- 3.7%, and HDL2 9.2 +/- 2.8%. Plasma and VLDL-IDL-associated LPS correlated positively, and LDL- and HDL-associated LPS negatively with clinical periodontal parameters and plasma cytokine concentrations. Mean plasma LPS activity increased after periodontal treatment from 44.0 +/- 17.0 to 55.7 +/- 24.2 EU/ml (P = 0.006). No significant changes were found in LPS lipoprotein distribution and lipoprotein compositions after the treatment.

CONCLUSIONS

Endotoxemia increases with severity of periodontitis. In periodontitis, LPS associates preferentially with the pro-atherogenic VLDL-IDL fraction. Periodontal treatment has only minor effects on plasma LPS activity or distribution, which reflects persistence of the disease.

Hyperhomocysteinemia induced by methionine supplementation does not independently cause atherosclerosis in C57BL/6J mice

A causal relationship between diet-induced hyperhomocysteinemia (HHcy) and accelerated atherosclerosis has been established in apolipoprotein E-deficient (apoE(-/-)) mice. However, it is not known whether the proatherogenic effect of HHcy in apoE(-/-) mice is independent of hyperlipidemia and/or deficiency of apoE. In this study, a comprehensive dietary approach using C57BL/6J mice was used to investigate whether HHcy is an independent risk factor for accelerated atherosclerosis or dependent on additional dietary factors that increase plasma lipids and/or inflammation. C57BL/6J mice at 4 wk of age were divided into 6 dietary groups: chow diet (C), chow diet + methionine (C+M), western-type diet (W), western-type diet + methionine (W+M), atherogenic diet (A), or atherogenic diet + methionine (A+M). After 2, 10, 20, or 40 wk on the diets, mice were sacrificed, and the levels of total plasma homocysteine, cysteine, and glutathione, as well as total plasma cholesterol and triglycerides were analyzed. Aortic root sections were examined for atherosclerotic lesions. HHcy was induced in all groups supplemented with methionine, compared to diet-matched control groups. Plasma total cholesterol was significantly increased in mice fed the W or A diet. However, the W diet increased LDL/IDL and HDL levels, while the A diet significantly elevated plasma VLDL and LDL/IDL levels without increasing HDL. No differences in plasma total cholesterol levels or lipid profiles were observed between methionine-supplemented groups and the diet-matched control groups. Early atherosclerotic lesions containing macrophage foam cells were only observed in mice fed the A or A + M diet. Furthermore, lesion size was significantly larger in the A + M group compared to the A group at 10 and 20 wk; however, mature lesions were never observed even after 40 wk on these diets. The presence of lymphocytes, increased hyaluronan staining, and the expression of endoplasmic reticulum (ER) stress markers were also increased in atherosclerotic lesions from the A + M group. Taken together, these results suggest that HHcy does not independently cause atherosclerosis in C57BL/6J mice even in the presence of increased total plasma lipids induced by the W diet. However, HHcy can accelerate atherosclerotic lesion development under dietary conditions that increase plasma VLDL levels and/or inflammation.

Carbenoxolone treatment attenuates symptoms of metabolic syndrome and atherogenesis in obese, hyperlipidemic mice

Glucocorticoids, which are well established to regulate body fat mass distribution, adipocyte lipolysis, hepatic gluconeogenesis, and hepatocyte VLDL secretion, are speculated to play a role in the pathology of metabolic syndrome. Recent focus has been on the activity of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which is capable of regenerating, and thus amplifying, glucocorticoids in key metabolic tissues such as liver and adipose tissue. To determine the effects of global 11beta-HSD1 inhibition on metabolic syndrome risk factors, we subcutaneously injected "Western"-type diet-fed hyperlipidemic mice displaying moderate or severe obesity [LDL receptor (LDLR)-deficient (LDLR(-/-)) mice and mice derived from heterozygous agouti (A(y)/a) and homozygous LDLR(-/-) breeding pairs (A(y)/a;LDLR(-/-) mice)] with the nonselective 11beta-HSD inhibitor carbenoxolone for 4 wk. Body composition throughout the study, end-point fasting plasma, and extent of hepatic steatosis and atherosclerosis were assessed. This route of treatment led to detection of high levels of carbenoxolone in liver and fat and resulted in decreased weight gain due to reduced body fat mass in both mouse models. However, only A(y)/a;LDLR(-/-) mice showed an effect of 11beta-HSD1 inhibition on fasting insulin and plasma lipids, coincident with a reduction in VLDL due to mildly increased VLDL clearance and dramatically decreased hepatic triglyceride production. A(y)/a;LDLR(-/-) mice also showed a greater effect of the drug on reducing atherosclerotic lesion formation. These findings indicate that subcutaneous injection of an 11beta-HSD1 inhibitor allows for the targeting of the enzyme in not only liver, but also adipose tissue, and attenuates many metabolic syndrome risk factors, with more pronounced effects in cases of severe obesity and hyperlipidemia.

Activation of peroxisome proliferator-activated receptor-alpha by fenofibrate prevents myocardial dysfunction during endotoxemia in rats

OBJECTIVE

To investigate the effects of fenofibrate, an activator of peroxisome proliferator-activated receptor-alpha, on cardiac function in a rat endotoxemia model.

DESIGN

Prospective, randomized, controlled study.

SETTING

University research laboratory.

SUBJECTS

Three-month-old male Wistar rats.

INTERVENTIONS

Animals were fed with standard diet containing no drug or fenofibrate (0.2%) for 14 days. They were then injected intravenously with either 5 mg/kg lipopolysaccharide (LPS and fenofibrate + LPS groups) or saline (control and fenofibrate groups).

MEASUREMENTS AND MAIN RESULTS

In the LPS group, body weight loss, metabolic acidosis, and thrombocytopenia confirmed presence of systemic endotoxemia. LPS administration resulted in an early peak in plasma tumor necrosis factor-alpha, decreased cardiac contractility (isolated and perfused heart), reduced myofilament Ca2+ sensitivity (Triton-skinned cardiac fibers), and increased left ventricular nitric oxide (NO) end-oxidation products (NO(x) and NO2), without evidence of myocardial oxidative stress (thiobarbituric acid-reactive substances and antioxidant enzyme activities). Fenofibrate pretreatment (fenofibrate + LPS group) did not alter signs of endotoxemia but prevented reductions in both cardiac contractility and myofilament Ca2+ sensitivity. The peak of plasma tumor necrosis factor-alpha was attenuated, whereas myocardial NO(x) and NO2 remained similar to the LPS group. Oxidative stress was suggested from moderate increase in cardiac thiobarbituric acid-reactive substances and reduced glutathione peroxidase activity.

CONCLUSION

Fenofibrate, an activator of peroxisome proliferator-activated receptor-alpha, may prevent endotoxemia-induced cardiac dysfunction and reduction in myofilament Ca2+ sensitivity. Our data also suggest a mediating role for early peak plasma tumor necrosis factor-alpha, but not for myocardial NO production or oxidative stress.

Simvastatin stimulates macrophage interleukin-1β secretion through an isoprenylation-dependent mechanism

Statin treatment inhibits oxidized lipoprotein-induced intracellular lipid accumulation (foam cell formation) and reduces plasma levels of inflammatory markers such as interleukin-1beta (IL-1beta). The aim of the present study was to determine if simvastatin affected lipid accumulation in macrophages incubated with aggregated low density lipoproteins (AgLDL) and whether simvastatin had a direct effect on cytokine secretion from macrophages. Simvastatin treatment did not inhibit AgLDL-induced macrophage lipid accumulation, but significantly increased the secretion of IL-1beta and IL-8 from macrophages, whilst inhibiting the secretion of tumor necrosis factor-alpha (TNF-alpha) and having no significant effect on IL-6 secretion. Increased macrophage lipid content did not block statin-induced IL-1beta and IL-8 secretion. Simvastatin-stimulated IL-1beta secretion from macrophages was inhibited by isoprenoids. We therefore hypothesized that simvastatin stimulated IL-1beta secretion by affecting isoprenylation-dependent signaling pathways. Another possible mechanism for affecting such signaling is to impair isoprenoid transfer protein activity with specific inhibitors such as GGTI-297 and FTInhI. This treatment resulted in strong stimulation of IL-1beta secretion that was further enhanced when exogenous IL-1beta was present at the beginning of treatment. These data suggest an isoprenylation-dependent negative-feedback loop for macrophage IL-1beta secretion that is inhibited by statin treatment.

Inflammatory effects of very low-density lipoprotein and fatty acids

High plasma triacylglycerol (triglyceride, TG) levels is a risk factor for atherosclerosis. Very large lipoproteins, such as chylomicrons, alone are not considered atherogenic, but TG-rich remnant lipoproteins can penetrate into the vascular wall. Importantly, accumulating evidence suggests that all TG-rich lipoproteins stimulate cytokine expression in circulating monocytes. Very low-density lipoprotein (VLDL) stimulates monocyte adhesion to endothelial cells and expression of inflammatory genes in macrophages. Furthermore, fatty acids released from large lipoproteins can stimulate both vascular cells and circulating monocytes. It is likely that fatty acids released from TG-rich lipoproteins contribute to atherogenesis, but the role of fatty acids in ischemic heart disease is not as direct as that of cholesterol. Fatty acids influence plasma lipoprotein levels and either stimulate or suppress numerous cellular functions relevant to atherogenesis. While certain n-3 fatty acids are good for health, most other medium- to long-chain fatty acids appear to promote inflammation in cell culture studies and need to be studied further. Nevertheless, the existing evidence supports the general conclusion that TG-rich lipoproteins and fatty acids greatly accelerate the progression of atherosclerosis. This may be because of their inflammatory effects.

The role of lipolysis in mediating the proinflammatory effects of very low density lipoproteins in mouse peritoneal macrophages

Hypertriglyceridemia is an important risk factor for atherosclerosis, especially in obesity. Macrophages are one of the primary cell types involved in atherogenesis and are thought to contribute to lesion formation through both lipid accumulation and proinflammatory gene expression. In this study, we sought to determine the direct impact of triglyceride (TG)-rich VLDL-induced lipid accumulation on macrophage proinflammatory processes. Incubation of mouse peritoneal macrophages with 100 microg/ml VLDL for 6 h led to 2.8- and 3.7-fold increases in intracellular TGs and FFAs, respectively (P < 0.05). The inflammatory proteins tumor necrosis factor-alpha, interleukin-1beta, monocyte chemoattractant protein-1, intercellular adhesion molecule-1, matrix metalloproteinase 3 (MMP3), and macrophage inflammatory protein-1alpha (MIP-1alpha) were all upregulated by at least 2-fold (P < 0.05) in a dose-dependent manner in VLDL-treated macrophages. The increase in inflammatory gene expression coincided with the phosphorylation of the mitogen-activated protein kinase (MAPK) pathway members extracellular signal-regulated kinase (ERK) 1/2, stress-activated protein kinase/c-Jun NH2-terminal kinase, and p38 MAPK and was ameliorated by U0126, an inhibitor of ERK1/2. Inhibition of extracellular TG hydrolysis with tetrahydrolipstatin (Orlistat) resulted in the absence of intracellular TG and FFA accumulation and was accompanied by the amelioration of ERK1/2 phosphorylation and MIP-1alpha gene expression. These data indicate that VLDL hydrolysis, and the subsequent accumulation of intracellular FFAs and TGs, plays a substantive role in mediating the proinflammatory effects of VLDL. These data have important implications for the direct proatherogenic effects of VLDL on macrophage-driven atherosclerosis.

Very low-density lipoprotein induces interleukin-1β expression in macrophages

Elevated plasma level of very low-density lipoprotein (VLDL) is a risk factor for coronary heart disease. We investigated the effect of VLDL on expression of the pro-inflammatory cytokine interleukin-1beta (IL-1beta) in human peripheral blood monocyte-derived macrophages. IL-1beta mRNA and protein expression was analysed by PCR and ELISA, respectively. Caspase activation was assessed by immunoblotting. Apart from potentiating lipopolysaccharide-induced secretion of IL-1beta, VLDL alone induced secretion of IL-1beta from human monocyte-derived macrophages. This effect was suppressed by an inhibitor of caspase-1, the protease which cleaves pro-IL-1beta. VLDL treatment activated caspase-1, as indicated by increased levels of the caspase-1 p20 subunit. Furthermore, VLDL increased IL-1beta mRNA expression, which was associated with activation of transcription factor AP-1. Inhibition of caspase-1 did not influence IL-1beta mRNA expression. In conclusion, VLDL induces IL-1beta mRNA expression, caspase-1 activation, and IL-1beta release from macrophages, suggesting that VLDL can promote inflammation in atherosclerotic lesions.