Sol Sherry lecture in thrombosis: molecular events in acute inflammation

Atorvastatin and blood flow regulate expression of distinctive sets of genes in mouse carotid artery endothelium

Hypercholesterolemia is a well-known pro-atherogenic risk factor and statin is the most effective anti-atherogenic drug that lowers blood cholesterol levels. However, despite systemic hypercholesterolemia, atherosclerosis preferentially occurs in arterial regions exposed to disturbed blood flow (d-flow), while the stable flow (s-flow) regions are spared. Given their predominant effects on endothelial function and atherosclerosis, we tested whether (1) statin and flow regulate the same or independent sets of genes and (2) statin can rescue d-flow-regulated genes in mouse artery endothelial cells in vivo. To test the hypotheses, C57BL/6 J mice (8-week-old male, n=5 per group) were pre-treated with atorvastatin (10mg/kg/day, Orally) or vehicle for 5 days. Thereafter, partial carotid ligation (PCL) surgery to induce d-flow in the left carotid artery (LCA) was performed, and statin or vehicle treatment was continued. The contralateral right carotid artery (RCA) remained exposed to s-flow to be used as the control. Two days or 2 weeks post-PCL surgery, endothelial-enriched RNAs from the LCAs and RCAs were collected and subjected to microarray gene expression analysis. Statin treatment in the s-flow condition (RCA+statin versus RCA+vehicle) altered the expression of 667 genes at 2-day and 187 genes at 2-week timepoint, respectively (P<0.05, fold change (FC)≥±1.5). Interestingly, statin treatment in the d-flow condition (LCA+statin versus LCA+vehicle) affected a limited number of genes: 113 and 75 differentially expressed genes at 2-day and 2-week timepoint, respectively (P<0.05, FC≥±1.5). In contrast, d-flow in the vehicle groups (LCA+vehicle versus RCA+vehicle) differentially regulated 4061 genes at 2-day and 3169 genes at 2-week timepoint, respectively (P<0.05, FC≥±1.5). Moreover, statin treatment did not reduce the number of flow-sensitive genes (LCA+statin versus RCA+statin) compared to the vehicle groups: 1825 genes at 2-day and 3788 genes at 2-week, respectively, were differentially regulated (P<0.05, FC≥±1.5). These results revealed that both statin and d-flow regulate expression of hundreds or thousands of arterial endothelial genes, respectively, in vivo. Further, statin and d-flow regulate independent sets of endothelial genes. Importantly, statin treatment did not reverse d-flow-regulated genes except for a small number of genes. These results suggest that both statin and flow play important independent roles in atherosclerosis development and highlight the need to consider their therapeutic implications for both.

Toll-like receptors in the functional orientation of cardiac progenitor cells

Cardiac progenitor cells (CPCs) have the potential to differentiate into several cell lineages with the ability to restore in cardiac tissue. Multipotency and self-renewal activity are the crucial characteristics of CPCs. Also, CPCs have promising therapeutic roles in cardiac diseases such as valvular disease, thrombosis, atherosclerosis, congestive heart failure, and cardiac remodeling. Toll-like receptors (TLRs), as the main part of the innate immunity, have a key role in the development and differentiation of immune cells. Some reports are found regarding the effect of TLRs in the maturation of stem cells. This article tried to find the potential role of TLRs in the dynamics of CPCs. By showing possible crosstalk between the TLR signaling pathways and CPCs dynamics, we could achieve a better conception related to TLRs in the regeneration of cardiac tissue.

Low expression of PRMT5 in peripheral blood may serve as a potential independent risk factor in assessments of the risk of stable CAD and AMI

Background

Protein arginine methyltransferases (PRMTs) can catalyse the methylation of arginine and participate in many important cellular reaction processes. The purpose of this research is to determine whether the expression levels of the PRMT5 gene in peripheral blood can be used as a biomarker for predicting the risk of Acute Myocardial Infarction (AMI).

Methods

In this research, peripheral blood was collected from 91 patients with AMI and 87 patients with stable coronary artery disease (CAD). Real-time fluorescent quantitative PCR was performed to measure the expression levels of the PRMT5 gene at the mRNA level, and a western blot analysis was performed to measure the expression levels of the PRMT5 gene at the protein level.

Results

The results indicate that at both the RNA and protein levels, the expression levels of the PRMT5 gene in peripheral blood from patients with AMI are significantly lower than those in peripheral blood from patients with stable CAD (Z = − 4.813, P = 0.000). The low expression of the PRMT5 gene is relevant to the Gensini score of the coronary artery (rs = − 0.205, P = 0.015) but is irrelevant to the serum level of blood lipids, level of cardiac troponin (rs = − 0.125, P = 0.413) and time intervals of occurrence (rs = − 0.146, P = 0.211). Patients who have a low PRMT5 expression in the peripheral blood are 5.472 times more likely to suffer from AMI than other patients.

Conclusion

Compared to stable CAD patients, AMI patients have a lower expression of the PRMT5 gene in their peripheral blood. Patients who have low PRMT5 gene expression in the peripheral blood are more likely to suffer from AMI than those with stable CAD. A low expression of the PRMT5 gene serves as an independent risk factor for the occurrence of AMI.

Cardioprotective and Anti-Aggregatory Effects of Levosimendan on Isoproterenol-Induced Myocardial Injury in High-Fat-Fed Rats Involves Modulation of PI3K/Akt/mTOR Signaling Pathway and Inhibition of Apoptosis

Hyperlipidemia and hypercoagulability states are linked with the increased risks of myocardial infarction (MI). Levosimendan has vasorelaxant and anti-aggregatory properties. The present study evaluated the anti-aggregatory and cardioprotective effects of levosimendan versus cilostazol in high-fat diet (HFD)-fed rats subjected to isoproterenol-induced MI. Rats were assigned to normal, HFD, HFD + isoproterenol, HFD + isoproterenol + cilostazol, and HFD + isoproterenol + levosimendan. The present study investigated the anti-aggregatory effect of both levosimendan and cilostazol and revealed that both drugs attenuated the severity of platelet aggregation. Moreover, both levosimendan and cilostazol revealed effectiveness in attenuating the severity of HFD/isoproterenol-induced myocardial injury as revealed by electrocardiogram signs, apoptotic markers, and histopathological score via counteracting the oxidative stress burden, increments in the expression of inflammatory mediators, and modulating nuclear factor kappa-B (NF-κB) and phosphatidylinositide 3-kinases (PI3K)/protein kinase B (Akt)/ mechanistic target of rapamycin (mTOR) pathway. It was obvious that levosimendan offered more cardioprotective properties than cilostazol. The study showed the relations between hyperlipedemia, hyperaggregability state, and myocardial injury with the modulation of NF-κB and PI3K/Akt/mTOR pathway.

Anti-aggregatory effect of boswellic acid in high-fat fed rats: involvement of redox and inflammatory cascades

INTRODUCTION

A high-fat diet is one of the main dietary factors promoting platelet aggregation. The present study was conducted to elucidate the involvement of boswellic acid (BA) on the platelet hyperaggregability in HFD-fed rats. As platelet hyperaggregability in HFD rats is closely linked to inflammation and enhanced free radical production, the present study was extended to evaluate the anti-inflammatory and anti-oxidative effect of BA on HFD-promoted platelet aggregation.

MATERIAL AND METHODS

Rats were assigned to normal, HFD-fed, aspirin-treated (30 mg/kg), and BA-treated (250 and 500 mg/kg) groups.

RESULTS

Boswellic acid administration in a high dose was effective in attenuating the severity of hyperlipidemia and platelet aggregation, indicated by lower collagen/epinephrine-induced platelet aggregation, as evidenced by the significant increase (p < 0.05) in the circulating platelet count and reduction in the number of thrombi in the lungs. Moreover, it attenuated the oxidative stress and the intensity of inflammatory mediators associated with platelet hyperaggregability, as evidenced by the inhibitory effects on interlukin-1β, COX-2 and tumor necrosis factor-α, indicating that the antiplatelet activity of BA is likely a consequence of controlling oxidative stress and inflammation.

CONCLUSIONS

The present data suggest that BA shows a promising anti-aggregatory effect by attenuating the enhanced hyperlipidemia, oxidative stress and inflammation associated with HFD.

Mice with Genetic Deletion of Group VIA Phospholipase A2β Exhibit Impaired Macrophage Function and Increased Parasite Load in Trypanosoma cruzi-Induced Myocarditis

Trypanosoma cruzi infection, which is the etiological agent of Chagas disease, is associated with intense inflammation during the acute and chronic phases. The pathological progression of Chagas disease is influenced by the infiltration and transmigration of inflammatory cells across the endothelium to infected tissues, which are carefully regulated processes involving several molecular mediators, including adhesion molecules and platelet-activating factor (PAF). We have shown that PAF production is dependent upon calcium-independent group VIA phospholipase A2β (iPLA2β) following infection of human coronary artery endothelial cells (HCAECs) with T. cruzi, suggesting that the absence of iPLA2β may decrease the recruitment of inflammatory cells to the heart to manage parasite accumulation. Cardiac endothelial cells isolated from iPLA2β-knockout (iPLA2β-KO) mice infected withT. cruzi demonstrated decreased PAF production compared to that by cells isolated from wild-type (WT) mice but demonstrated increases in adhesion molecule expression similar to those seen in WT mice. Myocardial inflammation in iPLA2β-KO mice infected with T. cruzi was similar in severity to that in WT mice, but the iPLA2β-KO mouse myocardium contained more parasite pseudocysts. Upon activation, macrophages from iPLA2β-KO mice produced significantly less nitric oxide (NO) and caused lessT. cruzi inhibition than macrophages from wild-type mice. Thus, the absence of iPLA2β activity does not influence myocardial inflammation, but iPLA2β is essential forT. cruzi clearance.

Relation Between Circulating Inflammatory Chemokines and Vascular Characteristics in Healthy, Young Children

BACKGROUND

Atherosclerosis begins in childhood with the occurrence of inflammatory vascular wall alterations that are detectable with B-mode ultrasound. Chemokines appear to be involved in the development of these alterations given that they occur early in the atherosclerotic pathway as mediators of vascular inflammation. However, this has not extensively been investigated. Therefore, we studied in healthy young children whether chemokines monocyte chemotactic protein 1 (MCP-1), regulated on activation normal T-cell expressed and secreted (RANTES), and vascular and intercellular adhesion molecules (VCAM and ICAM) related to vascular characteristics of the carotid artery.

METHODS AND RESULTS

We obtained demography, anthropometry, and overnight fasting plasma of 139 eight-year-old children of the Wheezing Illnesses Study Leidsche Rijn birth cohort. Carotid intima-media thickness (CIMT), distensibility, and Young's Elastic Modulus (YEM) of the common carotid artery were measured sonographically. Chemokine plasma levels were assessed using a multiplex assay. We studied the relation between the chemokines and vascular characteristics using multivariable linear regression analyses with adjustments for sex, systolic blood pressure, homeostasis model assessment of insulin resistance, triglycerides, low-density lipoprotein- and high-density lipoprotein-cholesterol. Of the studied chemokines, RANTES related to common carotid distensibility and YEM. One standard deviation increase in RANTES level related to a 5.45-MPA(-1) (95% confidence interval [CI], -9.43, -1.39; P=0.01) decrease in distensibility and to a 5.55-kPa increase in YEM (95% CI, 0.40, 10.85; P=0.03). RANTES did not relate to CIMT. MCP-1, VCAM, and ICAM did not relate to any of the studied vascular characteristics.

CONCLUSION

RANTES appears to be involved in the development of preatherosclerotic inflammatory vascular alterations already in healthy, young children. This may provide further insight into the early-life origins of atherosclerosis.

Higher plasma platelet-activating factor levels are associated with increased risk of vertebral fracture and lower bone mineral density in postmenopausal women

Despite experimental and animal evidence showing the detrimental effects of platelet-activating factor (PAF) on bone metabolism, there are no clinical studies relating PAF to osteoporosis-related phenotypes. This case-control study investigates the association between plasma PAF, osteoporotic vertebral fracture (VF), and bone mineral density (BMD) in postmenopausal Korean women. Among 474 eligible women not taking any drug or having any disease that could affect bone metabolism, we identified 73 cases defined as subjects with radiological VF. The controls were randomly selected from the remaining 401 subjects and matched 1:1 to cases in terms of both age and body mass index (BMI). Lateral thoracolumbar radiographs, BMD, and plasma PAF levels were determined for all subjects. Postmenopausal women with VF demonstrated 34.6 % higher plasma PAF levels than subjects without VF after adjusting for age, BMI, smoking habits, alcohol intake, regular exercise, and parental history of osteoporotic fractures (P = 0.021). Multiple logistic regression analyses revealed that the odds ratio for VF linearly increased across increasing PAF quartiles (P for trend = 0.040) and the odds for VF were 2.88-fold higher in subjects in the highest quartile in comparison with those in the lowest quartile (95 % CI 1.04-8.01). Plasma PAF levels were inversely correlated with BMD at various sites (γ = -0.253 to -0.176, P = 0.003-0.041). These findings suggest that plasma PAF may be a potential biomarker for predicting poor bone health in postmenopausal women.

Human neutrophil formyl peptide receptor phosphorylation and the mucosal inflammatory response

Bacterial/mitochondrial fMLF analogs bind FPR1, driving accumulation/activation of PMN at sites of infection/injury, while promoting wound healing in epithelia. We quantified levels of UFPR1 and TFPR1 in isolated PMN by use of phosphosensitive NFPRb and phosphorylation-independent NFPRa antibodies. UFPR1 and total TFPR were assessed inflamed mucosa, observed in human IBD. In isolated PMN after fMLF stimulation, UFPR1 declined 70% ((fMLF)EC50 = 11 ± 1 nM; t1/2 = 15 s) and was stable for up to 4 h, whereas TFPR1 changed only slightly. Antagonists (tBoc-FLFLF, CsH) and metabolic inhibitor NaF prevented the fMLF-dependent UFPR1 decrease. Annexin A1 fragment Ac2-26 also induced decreases in UFPR1 ((Ac2-26)EC50 ∼ 3 µM). Proinflammatory agents (TNF-α, LPS), phosphatase inhibitor (okadaic acid), and G-protein activator (MST) modestly increased (fMLF)EC50, 2- to 4-fold, whereas PTX, Ca(2+) chelators (EGTA/BAPTA), H2O2, GM-CSF, ENA-78, IL-1RA, and LXA4 had no effect. Aggregation-inducing PAF, however, strongly inhibited fMLF-stimulated UFPR1 decreases. fMLF-driven PMN also demonstrated decreased UFPR1 after traversing monolayers of cultured intestinal epithelial cells, as did PMN in intestinal mucosal samples, demonstrating active inflammation from UC patients. Total TFPR remained high in PMN within inflamed crypts, migrating through crypt epithelium, and in the lamina propria-adjoining crypts, but UFPR1 was only observed at some peripheral sites on crypt aggregates. Loss of UFPR1 in PMN results from C-terminal S/T phosphorylation. Our results suggest G protein-insensitive, fMLF-dependent FPR1 phosphorylation in isolated suspension PMN, which may manifest in fMLF-driven transmigration and potentially, in actively inflamed tissues, except at minor discrete surface locations of PMN-containing crypt aggregates.

Chronic ethanol ingestion induces oxidative kidney injury through taurine-inhibitable inflammation

Chronic ethanol ingestion mildly damages liver through oxidative stress and lipid oxidation, which is ameliorated by dietary supplementation with the anti-inflammatory β-amino acid taurine. Kidney, like liver, expresses cytochrome P450 2E1 that catabolizes ethanol with free radical formation, and so also may be damaged by ethanol catabolism. Sudden loss of kidney function, and not liver disease itself, foreshadows mortality in patients with alcoholic hepatitis [J. Altamirano, Clin. Gastroenterol. Hepatol. 2012, 10:65]. We found that ethanol ingestion in the Lieber-deCarli rat model increased kidney lipid oxidation, 4-hydroxynonenal protein adduction, and oxidatively truncated phospholipids that attract and activate leukocytes. Chronic ethanol ingestion increased myeloperoxidase-expressing cells in kidney and induced an inflammatory cell infiltrate. Apoptotic terminal deoxynucleotidyl transferase nick-end labeling-positive cells and active caspase-3 increased in kidney after ethanol ingestion, with reduced filtration with increased circulating blood urea nitrogen (BUN) and creatinine. These events were accompanied by release of albumin, myeloperoxidase, and the acute kidney injury biomarkers kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin, and cystatin c into urine. Taurine sequesters HOCl from myeloperoxidase of activated leukocytes, and taurine supplementation reduced renal lipid oxidation, reduced leukocyte infiltration, and reduced the increase in myeloperoxidase-positive cells during ethanol feeding. Taurine supplementation also normalized circulating BUN and creatinine levels and suppressed enhanced myeloperoxidase, albumin, KIM-1, and cystatin c in urine. Thus, chronic ethanol ingestion oxidatively damages kidney lipids and proteins, damages renal function, and induces acute kidney injury through an inflammatory cell infiltrate. The anti-inflammatory nutraceutical taurine effectively interrupts this ethanol-induced inflammatory cycle in kidney.

Absence of calcium-independent phospholipase A2 β impairs platelet-activating factor production and inflammatory cell recruitment in Trypanosoma cruzi-infected endothelial cells

Both acute and chronic phases of Trypanosoma cruzi (T. cruzi) infection are characterized by tissue inflammation, mainly in the heart. A key step in the inflammatory process is the transmigration of inflammatory cells across the endothelium to underlying infected tissues. We observed increased arachidonic acid release and platelet-activating factor (PAF) production in human coronary artery endothelial cells (HCAEC) at up to 96 h of T. cruzi infection. Arachidonic acid release is mediated by activation of the calcium-independent phospholipase A2 (iPLA2) isoforms iPLA2 β and iPLA2 γ, whereas PAF production was dependent upon iPLA2 β activation alone. Trypanosoma cruzi infection also resulted in increased cell surface expression of adhesion molecules. Increased adherence of inflammatory cells to T. cruzi-infected endothelium was blocked by inhibition of endothelial cell iPLA2 β or by blocking the PAF receptor on inflammatory cells. This suggests that PAF, in combination with adhesion molecules, might contribute to parasite clearing in the heart by recruiting inflammatory cells to the endothelium.

Immune effector mechanisms implicated in atherosclerosis: from mice to humans

According to the traditional view, atherosclerosis results from a passive buildup of cholesterol in the artery wall. Yet, burgeoning evidence implicates inflammation and immune effector mechanisms in the pathogenesis of this disease. Both innate and adaptive immunity operate during atherogenesis and link many traditional risk factors to altered arterial functions. Inflammatory pathways have become targets in the quest for novel preventive and therapeutic strategies against cardiovascular disease, a growing contributor to morbidity and mortality worldwide. Here we review current experimental and clinical knowledge of the pathogenesis of atherosclerosis through an immunological lens and how host defense mechanisms essential for survival of the species actually contribute to this chronic disease but also present new opportunities for its mitigation.

Platelet-activating factor receptor blockade ameliorates Aggregatibacter actinomycetemcomitans-induced periodontal disease in mice

Periodontal disease (PD) is a chronic inflammatory and alveolar bone destructive disease triggered by oral biofilm-producing microorganisms, such as Aggregatibacter actinomycetemcomitans. The levels of the phospholipid platelet-activating factor (PAF) in the saliva, gingival crevicular fluid, and periodontal tissues are significantly increased during inflammatory conditions, such as PD, but the exact mechanism that links PAF to alveolar bone resorption is not well understood. In the current study, alveolar bone resorption was induced by experimental PD through the oral inoculation of A. actinomycetemcomitans in wild-type (WT) and PAF receptor knockout (Pafr(-/-)) mice. In vitro experiments using A. actinomycetemcomitans lipopolysaccharide (LPS)-stimulated RAW 264.7 cells treated with a PAF receptor antagonist (UK74505) were also performed. The expression of lyso-PAF acetyltransferase in periodontal tissues was significantly increased 3 h after A. actinomycetemcomitans LPS injection in mice. WT and Pafr(-/-) mice that were subjected to oral inoculation of A. actinomycetemcomitans presented neutrophil accumulation and increased levels of CXCL-1 and tumor necrosis factor alpha (TNF-α) in periodontal tissues. However, Pafr(-/-) mice presented less alveolar bone loss than WT mice. The in vitro blockade of the PAF receptor impaired the resorptive activity of A. actinomycetemcomitans LPS-activated osteoclasts. In conclusion, this study shows for the first time that the blockade of PAF receptor may contribute to the progression of PD triggered by A. actinomycetemcomitans by directly affecting the differentiation and activity of osteoclasts.

Lipoteichoic acid isolated from Lactobacillus plantarum suppresses LPS-mediated atherosclerotic plaque inflammation

Chronic inflammation plays an important role in atherogenesis. Experimental studies have demonstrated the accumulation of monocytes/macrophages in atherosclerotic plaques caused by inflammation. Here, we report the inhibitory effects of lipoteichoic acid (LTA) from Lactobacillus plantarum (pLTA) on atherosclerotic inflammation. pLTA inhibited the production of proinflammatory cytokines and nitric oxide in lipopolysaccharide (LPS)-stimulated cells and alleviated THP-1 cell adhesion to HUVEC by down-regulation of adhesion molecules such as intracellular adhesion molecule-1 (ICAM-I), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. The inhibitory effect of pLTA was mediated by inhibition of NF-κB and activation of MAP kinases. Inhibition of monocyte/macrophage infiltration to the arterial lumen was shown in pLTA-injected ApoE(-/-) mice, which was concurrent with inhibition of MMP-9 and preservation of CD31 production. The antiinflammatory effect mediated by pLTA decreased expression of atherosclerotic markers such as COX-2, Bax, and HSP27 and also cell surface receptors such as TLR4 and CCR7. Together, these results underscore the role of pLTA in suppressing atherosclerotic plaque inflammation and will help in identifying targets with therapeutic potential against pathogen-mediated atherogenesis.

Polyvalent choline phosphate as a universal biomembrane adhesive

Phospholipids in the cell membranes of all eukaryotic cells contain phosphatidyl choline (PC) as the headgroup. Here we show that hyperbranched polyglycerols (HPGs) decorated with the 'PC-inverse' choline phosphate (CP) in a polyvalent fashion can electrostatically bind to a variety of cell membranes and to PC-containing liposomes, the binding strength depending on the number density of CP groups per macromolecule. We also show that HPG-CPs can cause cells to adhere with varying affinity to other cells, and that binding can be reversed by subsequent exposure to low molecular weight HPGs carrying small numbers of PCs. Moreover, PC-rich membranes adsorb and rapidly internalize fluorescent HPG-CP but not HPG-PC molecules, which suggests that HPG-CPs could be used as drug-delivery agents. CP-decorated polymers should find broad use, for instance as tissue sealants and in the self-assembly of lipid nanostructures.

Lung endothelial cell platelet-activating factor production and inflammatory cell adherence are increased in response to cigarette smoke component exposure

An early event in the pathogenesis of emphysema is the development of inflammation associated with accumulation of polymorphonuclear leukocytes (PMN) in small airways, and inflammatory cell recruitment from the circulation involves migration across endothelial and epithelial cell barriers. Platelet-activating factor (PAF) promotes transendothelial migration in several vascular beds, and we postulated that increased PAF production in the airways of smokers might enhance inflammatory cell recruitment and exacerbate inflammation. To examine this possibility, we incubated human lung microvascular endothelial cells (HMVEC-L) with cigarette smoke extract (CSE) and found that CSE inhibits PAF-acetylhydrolase (PAF-AH) activity. This enhances HMVEC-L PAF production and PMN adherence, and adherence is blocked by PAF receptor antagonists (CV3988 or ginkgolide B). CSE also inhibited PAF-AH activity of lung endothelial cells isolated from wild-type (WT) and iPLA(2)β knockout mice, and with WT cells, CSE enhanced PAF production and RAW 264.7 cell adherence. In contrast, CSE did not affect PAF production or RAW 264.7 cell adherence to iPLA(2)β-null cells, suggesting that iPLA(2)β plays an important role in PAF production by lung endothelial cells. These findings suggest that inhibition of PAF-AH by components of cigarette smoke may initiate or exacerbate inflammatory lung disease by enhancing PAF production and promoting accumulation of inflammatory cells in small airways. In addition, iPLA(2)β is identified as a potential target for therapeutic interventions to reduce airway inflammation and the progression of chronic lung disease.

In vitro anti-inflammatory effects of naturally-occurring compounds from two Lauraceae plants

The in vitro anti-inflammatory effects of seven known lignans and one dihydrochalcone isolated from the leaves of two Lauraceae species (Pleurothyrium cinereum and Ocotea macrophylla), were evaluated through the inhibition of COX-1, COX-2, 5-LOX and the aggregation of rabbit platelets induced by PAF, AA and ADP. (+)-de-4"-O-methylmagnolin 4 was found to be a potent COX-2/5-LOX dual inhibitor and PAF-antagonist (COX-2 IC(50) 2.27 µM; 5-LOX IC(50) 5.05 µM; PAF IC(50) 2.51 µM). However, all compounds exhibited an activity at different levels, indicating good anti-inflammatory properties to be considered in further structural optimization studies.

Antioxidative defense enzymes in placenta protect placenta and fetus in inherited thrombophilia from hydrogen peroxide

Our aim was to investigate the activities of antioxidative defense enzymes in the placenta, fetal blood and amnion fluid in inherited thrombophilia. Thrombophilia was associated with nearly threefold increase of activity (p < 0.001) of the placental catalase (81.1 ± 20.6 U/mg of proteins in controls and 270.0 ± 69.9 U/mg in thrombophilic subjects), glutathione (GSH) peroxidase (C: 20.2 ± 10.1 U/mg; T: 60.0 ± 15.5 U/mg), and GSH reductase (C: 28.9 ± 5.6 U/mg; T: 72.7 ± 23.0 U/mg). The placental activities of superoxide dismutating enzymes—MnSOD and CuZnSOD, did not differ in controls and thrombophilia. Likewise, the activities of catalase and SOD in the fetal blood, and the level of ascorbyl radical which represents a marker of oxidative status of amniotic fluid, were similar in controls and thrombophilic subjects. From this we concluded that in thrombophilia, placental tissue is exposed to H₂O₂-mediated oxidative stress, which could be initiated by pro-thrombic conditions in maternal blood. Increased activity of placental H₂O₂-removing enzymes protects fetus and mother during pregnancy, but may increase the risk of postpartum thrombosis.

Activation of group VI phospholipase A2 isoforms in cardiac endothelial cells

The endothelium comprises a cellular barrier between the circulation and tissues. We have previously shown that activation of protease-activated receptor 1 (PAR-1) and PAR-2 on the surface of human coronary artery endothelial cells by tryptase or thrombin increases group VIA phospholipase A(2) (iPLA(2)β) activity and results in production of multiple phospholipid-derived inflammatory metabolites. We isolated cardiac endothelial cells from hearts of iPLA(2)β-knockout (iPLA(2)β-KO) and wild-type (WT) mice and measured arachidonic acid (AA), prostaglandin I(2) (PGI(2)), and platelet-activating factor (PAF) production in response to PAR stimulation. Thrombin (0.1 IU/ml) or tryptase (20 ng/ml) stimulation of WT endothelial cells rapidly increased AA and PGI(2) release and increased PAF production. Selective inhibition of iPLA(2)β with (S)-bromoenol lactone (5 μM, 10 min) completely inhibited thrombin- and tryptase-stimulated responses. Thrombin or tryptase stimulation of iPLA(2)β-KO endothelial cells did not result in significant PAF production and inhibited AA and PGI(2) release. Stimulation of cardiac endothelial cells from group VIB (iPLA(2)γ)-KO mice increased PAF production to levels similar to those of WT cells but significantly attenuated PGI(2) release. These results indicate that cardiac endothelial cell PAF production is dependent on iPLA(2)β activation and that both iPLA(2)β and iPLA(2)γ may be involved in PGI(2) release.

Urothelial cell platelet-activating factor production mediated by calcium-independent phospholipase A2γ

OBJECTIVES

To determine the effect of phospholipase A(2) (PLA(2)) inhibitors on urothelial cell platelet-activating factor (PAF) production in response to tryptase stimulation.

METHODS

Urothelial cells isolated from normal human ureters were immortalized with the human papillomavirus type 16E6E7 cell line (TEU-2 cells). PLA(2) activity in TEU-2 cells was measured using (16:0, [(3)H]18:1) plasmenylcholine and phosphatidylcholine substrates in the presence and absence of calcium. [(3)H]PAF production was measured in TEU-2 cells prelabeled with [(3)H] acetic acid. PAF-acetylhydrolase activity was measured by determining the amount of [(3)H] acetate hydrolyzed from [(3)H]PAF incubated with TEU-2 cellular protein. Adherence of human polymorphonuclear leukocyte (PMN) to TEU-2 cells was assessed by measuring myeloperoxidase activity in adherent PMNs after incubation with TEU-2 cells.

RESULTS

Most PLA(2) activity measured in TEU-2 cells was determined to be membrane-associated, calcium-independent PLA(2) and selective for plasmenylcholine substrate. Stimulation of TEU-2 cells with tryptase results in increased production of PAF and increased PMN adherence that were inhibited completely by pretreatment with the membrane-associated, calcium-independent PLA(2)γ-selective inhibitor (R)-bromoenol lactone. Pretreatment with the cytosolic PLA(2) inhibitor methyl arachidonyl fluorophosphonate resulted in potentiation of tryptase-stimulated PAF production and PMN adherence to TEU-2 cells that is a result of PAF-acetylhydrolase inhibition.

CONCLUSIONS

Tryptase stimulation of TEU-2 cells results in activation of membrane-associated, calcium-independent PLA(2)γ, leading to an increase in PAF production and increased PMN adherence. Inhibition of TEU-2 cell PAF-acetylhydrolase activity with methyl arachidonyl fluorophosphonate potentiated tryptase-stimulated PAF production and PMN adherence.

Smoking and atherosclerotic cardiovascular disease: Part I: atherosclerotic disease process

The normal endothelium inhibits platelet and leukocyte adhesion to the vascular surface maintaining a balance of profibrinolytic and prothrombotic activity. Endothelial function is assessed largely as endothelium-dependent vasomotion, partly based on the assumption that impaired endothelium-dependent vasodilation reflects the alteration of important endothelial functions. Atherosclerotic risk factors, such as hypercholesterolemia, hypertension, diabetes and smoking, are associated with endothelial dysfunction. In the diseased endothelium, the balance between pro- and antithrombotic, pro- and anti-inflammatory, pro- and antiadhesive or pro- and antioxidant effects shifts towards a proinflammatory, prothrombotic, pro-oxidative and proadhesive phenotype of the endothelium. A common mechanism underlying endothelial dysfunction is related to the increased vascular production of reactive oxygen species. Recent studies suggest that inflammation per se, and C-reactive protein in particular, may contribute directly to endothelial dysfunction. The loss of endothelial integrity is a hallmark of atherosclerosis and the causal possible link between each individual risk factor, the development of atherosclerosis and the subsequent clinical events, such as myocardial infarction or stroke.

Smoking and atherosclerotic cardiovascular disease: part II: role of cigarette smoking in cardiovascular disease development

Potential mechanisms and biomarkers of atherosclerosis related to cigarette smoking - a modifiable risk factor for that disease - are discussed in this article. These include smoking-associated inflammatory markers, such as leukocytes, high-sensitivity C-reactive protein, serum amyloid A, ICAM-1 and IL-6. Other reviewed markers are indicative for smoking-related impairment of arterial endothelial function (transcapillary leakage of albumin, inhibition of endogenous nitric oxide synthase activity and reduced endothelium-dependent vasodilation) or point to oxidative stress caused by various chemicals (cholesterol oxidation, autoantibodies to oxidized low-density lipoprotein, plasma levels of malondialdehyde and F(2)-isoprostanes and reduced antioxidant capacity). Smoking enhances platelet aggregability, increases blood viscosity and shifts the pro- and antithrombotic balance towards increased coagulability (e.g., fibrinogen, von Willebrand factor, ICAM-1 and P-selectin). Insulin resistance is higher in smokers compared with nonsmokers, and hemoglobin A1c is dose-dependently elevated, as is homocysteine. Smoke exposure may influence the kinetics of markers with different response to transient or chronic changes in cigarette smoking behavior.

The impact of ezetimibe on endothelial function and other markers of cardiovascular risk

OBJECTIVE

To review the published literature characterizing the impact of ezetimibe-containing lipid-lowering regimens on endothelial function and other markers of cardiovascular risk and discuss the potential relevance of these effects to the clinical benefit of ezetimibe.

DATA SOURCES

A MEDLINE search (2000-August 2009) was completed using the key words ezetimibe, statins, endothelial function, flow-mediated dilation, pleiotropic, and inflammation to identify relevant literature. Bibliographies of identified literature were reviewed for additional references.

STUDY SELECTION AND DATA EXTRACTION

All clinical studies published in English that evaluated the effect of ezetimibe on ancillary endpoints of cardiovascular disease risk, including endothelial function, inflammation, thrombosis, and oxidative stress, were evaluated.

DATA SYNTHESIS

Recent studies in patients with coronary artery disease (CAD), heart failure, and hypercholesterolemia have demonstrated that treatment with ezetimibe for 4-12 weeks elicits no improvement of endothelial function or other measures of cardiovascular disease risk. In contrast, other studies have reported that ezetimibe improves endothelial function in certain patient populations, including those with rheumatoid arthritis, CAD with type 2 diabetes, and metabolic syndrome. However, the statin monotherapy comparator groups in these studies that yielded equivalent reductions in cholesterol were superior, or at least equivalent to, ezetimibe-containing regimens in the improvement of these ancillary endpoints.

CONCLUSIONS

Overall, the evidence to date suggests that administration of ezetimibe, either as monotherapy or in combination with a statin, exerts minimal beneficial effects on endothelial function and other ancillary measures of cardiovascular disease risk beyond those conferred by its cholesterol-lowering effects. Studies with larger sample sizes and follow-up beyond 12 weeks remain necessary to further define the impact of ezetimibe on the processes integral to the pathogenesis and progression of cardiovascular disease.

Polymorphonuclear leukocytes isolated from umbilical cord blood as a useful research tool to study adherence to cell monolayers

One of the initial steps in the inflammatory process involves the adherence and transmigration of circulating polymorphonuclear leukocytes (PMN) across the endothelial cell monolayer. One of the main constituents of the neutrophil phagosome that contributes to bacterial killing is myeloperoxidase (MPO) which can be measured spectrophotometrically, using hydrogen peroxide as a substrate, and hence can be used as an index to quantify neutrophil adherence. To evaluate whether PMN isolated from umbilical cord blood could be used for in vitro experiments to monitor neutrophil adherence, we compared the adherence to confluent endothelial and epithelial cell monolayers using PMN isolated from umbilical cord and adult peripheral blood. The extent of PMN adherence was assessed by measuring MPO activity. In initial experiments, we isolated PMN from umbilical cord and adult peripheral blood and measured MPO activity with respect to cell number and assay incubation times. Our data demonstrate that PMN obtained from either source had similar MPO activity and similar adherence to endothelial or epithelial cells. In conclusion, our data suggest that umbilical cord blood is a suitable source of leukocytes to examine PMN adherence in the setting of inflammation in a variety of disease processes.

Toll-like receptor-2 mediates diet and/or pathogen associated atherosclerosis: proteomic findings

Background

Accumulating evidence implicates a fundamental link between the immune system and atherosclerosis. Toll-like receptors are principal sensors of the innate immune system. Here we report an assessment of the role of the TLR2 pathway in atherosclerosis associated with a high-fat diet and/or bacteria in ApoE^+/− mice.

Methods and Results

To explore the role of TLR2 in inflammation- and infection-associated atherosclerosis, 10 week-old ApoE^+/−-TLR2^+/+, ApoE^+/−-TLR2^+/− and ApoE^+/−-TLR2^−/− mice were fed either a high fat diet or a regular chow diet. All mice were inoculated intravenously, once per week for 24 consecutive weeks, with 50 µl live Porphyromonas gingivalis (P.g) (10⁷ CFU) or vehicle (normal saline). Animals were euthanized 24 weeks after the first inoculation. ApoE^+/−-TLR2^+/+ mice showed a significant increase in atheromatous lesions in proximal aorta and aortic tree compared to ApoE^+/−-TLR2^+/− and ApoE^+/−-TLR2^−/− mice for all diet conditions. They also displayed profound changes in plaque composition, as evidenced by increased macrophage infiltration and apoptosis, increased lipid content, and decreased smooth muscle cell mass, all reflecting an unstable plaque phenotype. SAA levels from ApoE^+/−-TLR2^+/+ mice were significantly higher than from ApoE^+/−-TLR2^+/− and ApoE^+/−-TLR2^−/− mice. Serum cytokine analysis revealed increased levels of pro-inflammatory cytokines in ApoE^+/−-TLR2^+/+ mice compared to ApoE^+/−-TLR2^+/− and TLR2^−/− mice, irrespective of diet or bacterial challenge. ApoE^+/−-TLR2^+/+ mice injected weekly for 24 weeks with FSL-1 (a TLR2 agonist) also demonstrated significant increases in atherosclerotic lesions, SAA and serum cytokine levels compared to ApoE^+/−-TLR2^−/− mice under same treatment condition. Finally, mass-spectrometry (MALDI-TOF-MS) of aortic samples analyzed by 2-dimentional gel electrophoresis differential display, identified 6 proteins upregulated greater than 2-fold in ApoE^+/−-TLR2^+/+ mice fed the high fat diet and inoculated with P.g compared to any other group.

Conclusion

Genetic deficiency of TLR2 reduces diet- and/or pathogen-associated atherosclerosis in ApoE^+/− mice, along with differences in plaque composition suggesting greater structural stability while TLR-2 ligand-specific activation triggers atherosclerosis. The present data offers new insights into the pathophysiological pathways involved in atherosclerosis and paves the way for new pharmacological interventions aimed at reducing atherosclerosis.

Potential mechanism for recruitment and migration of CD133 positive cells to areas of vascular inflammation

OBJECTIVE

Mast cells are found in large numbers in atherosclerotic plaques. The present study was conducted to determine whether tryptase stimulation of human coronary artery endothelial cells (HCAEC) would lead to an increase in transmigration of CD133 positive cells (CD133+). In vitro these cells can differentiate into mast cells under the influence of specific cytokines and growth factors.

METHODS AND RESULTS

CD133+ cells were isolated from umbilical cord blood. They express mRNA for several adhesion molecules that are also utilized in neutrophil migration and can migrate across an HCAEC monolayer. Migration increased significantly when HCAEC were stimulated with tryptase and decreased when CD133+ cells were pretreated with CV3988, a platelet activating factor receptor (PTAFR) antagonist. Following long-term cell culture, these cells stained positively for the presence of tryptase, a mast cell enzyme.

CONCLUSION

CD133+ cells can be utilized as a mast cell precursor population. The transendothelial migration is facilitated by the presence of tryptase and may utilize the PAF/PTAFR interaction in a manner similar to that involved in neutrophil transmigration. Following transmigration, a subset of these progenitor cells may mature into mast cells in the subendothelial space and play a role in propagation of the inflammatory process in atherosclerosis.

Effect of chronic hepatitis C virus infection on inflammatory lipid mediators

BACKGROUND

Platelet-activating factor (PAF), a powerful phospholipid mediator of inflammation, is degraded by plasma PAF-acetyl-hydxolase (pPAF-AH), an enzyme which circulates in serum mainly in a complex with lipoproteins that confer its biological activity. Hepatitis C virus (HCV) is linked to lipoproteins in serum too. Reduced pPAF-AH activity was observed in several diseases, including systemic vasculitis.

AIM

To evaluate if chronic HCV infection could alter pPAF-AH physiological functions.

SUBJECTS

145 subjects were studied: 56 HCV- and 52 HBV-infected patients (pathologic controls); 37 healthy subjects (healthy controls).

METHODS

pPAF-AH activity, PAF and Apo B100 titers were determined in plasma; enzyme expression levels were evaluated in monocyte-derived macrophages. HCV-RNA was detected in plasma, peripheral blood mononuclear cells and liver samples.

RESULTS

HCV-infected patients showed an increase of PAF levels following a significant decrease of pPAF-AH activity. A recovery of pPAF-AH activity occurs only in patients who clear HCV after the antiviral treatment. Expression levels of pPAF-AH mRNA and Apo B100 titers were not modified in HCV patients in comparison to controls.

CONCLUSION

In light of these results, it is tempting to hypothesize that during chronic HCV infection, the PAF/pPAF-AH system may be altered and this condition may contribute to HCV-related vascular damage.

Oxidized phospholipids: From molecular properties to disease

Oxidized lipids are generated from (poly)unsaturated diacyl- and alk(en)ylacyl glycerophospholipids under conditions of oxidative stress. The great variety of reaction products is defined by the degree of modification, hydrophobicity, chemical reactivity, physical properties and biological activity. The biological activities of these compounds may depend on both, the recognition of the particular molecular structures by specific receptors and on the unspecific physical and chemical effects on their target systems (membranes, proteins). In this review, we aim at highlighting the molecular features that are essential for the understanding of the biological actions of pure oxidized phospholipids. Firstly, their chemical structures are described as a basis for an understanding of their physical and (bio)chemical properties in membrane- and protein-bound form. Secondly, the biological activities of oxidized phospholipids are discussed in terms of their unspecific effects on the membrane level as well as their potential interactions with specific targets (receptors) affecting a large set of (signaling) molecules. Finally, the role of oxidized phospholipids as important mediators in pathophysiology is discussed with emphasis on atherosclerosis.

Treatment With Ezetimibe Plus Low-Dose Atorvastatin Compared With Higher-Dose Atorvastatin Alone

OBJECTIVES

We sought to test the platelet inhibitory and anti-inflammatory effects of a higher statin dosage compared with combined treatment with ezetimibe plus a low statin dose.

BACKGROUND

Reducing the level of low-density lipoprotein cholesterol (LDL-C) with statins induces important pleiotropic effects such as platelet inhibition. An insufficient LDL-C reduction often is treated with ezetimibe, an intestinal cholesterol absorption inhibitor, in combination with a low statin dose. It is not known whether this combination therapy has the same pleiotropic effects as a statin monotherapy.

METHODS

Fifty-six patients with coronary artery disease were assigned randomly to receive either 40 mg/day of atorvastatin or 10 mg/day of ezetimibe plus 10 mg/day of atorvastatin for 4 weeks. The levels of LDL-C, platelet activation markers after stimulation, platelet aggregation, and plasma chemokine levels (i.e., regulated on activation normally T-cell expressed and secreted [RANTES]) were measured before and after changing lipid-lowering medication.

RESULTS

Platelet activation markers (P-selectin) after stimulation (adenosine diphosphate) were reduced by 40 mg/day of atorvastatin (-5.2 +/- 1.6 arbitrary units) but not by ezetimibe plus low-dose atorvastatin (2.1 +/- 1.8 arbitrary units; p < 0.005) despite a similar reduction of LDL-C (atorvastatin -1.01 +/- 0.18 mmol/l vs. ezetimibe plus atorvastatin -1.36 +/- 0.22 mmol/l, p = NS). Thrombin receptor-activating peptide-induced platelet aggregation as well as plasma RANTES levels were reduced by 40 mg/day of atorvastatin but not by ezetimibe plus low-dose atorvastatin.

CONCLUSIONS

Platelet reactivity and a proinflammatory chemokine were reduced more by the higher atorvastatin dose than by ezetimibe plus low-dose atorvastatin. In patients with coronary artery disease, it might be important to combine ezetimibe with higher statin dosages to benefit from cholesterol-independent pleiotropic effects.

Systemic hypothermia increases PAI-1 expression and accelerates microvascular thrombus formation in endotoxemic mice

Introduction

Hypothermia during sepsis significantly impairs patient outcome in clinical practice. Severe sepsis is closely linked to activation of the coagulation system, resulting in microthrombosis and subsequent organ failure. Herein, we studied whether systemic hypothermia accelerates microvascular thrombus formation during lipopolysacharide (LPS)-induced endotoxemia in vivo, and characterized the low temperature-induced endothelial and platelet dysfunctions.

Methods

Ferric-chloride induced microvascular thrombus formation was analyzed in cremaster muscles of hypothermic endotoxemic mice. Flow cytometry, ELISA and immunohistochemistry were used to evaluate the effect of hypothermia on endothelial and platelet function.

Results

Control animals at 37°C revealed complete occlusion of arterioles and venules after 759 ± 115 s and 744 ± 112 s, respectively. Endotoxemia significantly (p < 0.05) accelerated arteriolar and venular occlusion in 37°C animals (255 ± 35 s and 238 ± 58 s, respectively). This was associated with an increase of circulating endothelial activation markers, agonist-induced platelet reactivity, and endothelial P-selectin and plasminogen activator inhibitor (PAI)-1 expression. Systemic hypothermia of 34°C revealed a slight but not significant reduction of arteriolar (224 ± 35 s) and venular (183 ± 35 s) occlusion times. Cooling of the endotoxemic animals to 31°C core body temperature, however, resulted in a further acceleration of microvascular thrombus formation, in particular in arterioles (127 ± 29 s, p < 0.05 versus 37°C endotoxemic animals). Of interest, hypothermia did not affect endothelial receptor expression and platelet reactivity, but increased endothelial PAI-1 expression and, in particular, soluble PAI-1 antigen (sPAI-Ag) plasma levels.

Conclusion

LPS-induced endotoxemia accelerates microvascular thrombus formation in vivo, most probably by generalized endothelial activation and increased platelet reactivity. Systemic hypothermia further enhances microthrombosis in endotoxemia. This effect is associated with increased endothelial PAI-1 expression and sPAI-Ag in the systemic circulation rather than further endothelial activation or modulation of platelet reactivity.

Modifications of plasma platelet-activating factor (PAF)-acetylhydrolase/PAF system activity in patients with chronic hepatitis C virus infection

Hepatitis C virus (HCV) chronically infects about 200 million individuals worldwide and leads to severe liver and lymphatic diseases. HCV circulates in the serum, associated with apoB-containing lipoproteins. Platelet-activating factor (PAF), a pro-inflammatory mediator, is mainly modulated by plasma PAF-acetylhydrolase (pPAF-AH), associated with ApoB100-containing low-density lipoproteins (LDL). The aim of the study was to evaluate the potential effects of chronic HCV infection on the PAF/pPAF-AH system. HCV-RNA was detected in plasma, peripheral blood mononuclear cells (PBMC) and liver samples. Plasma PAF levels, pPAF-AH activity, ApoB100 serum titres and pPAF-AH mRNA levels in cultured macrophages were determined. Plasma PAF levels were significantly higher and pPAF-AH activity was significantly lower in HCV patients than in controls. No significant modifications of pPAF-AH mRNA in macrophages or in ApoB100 values were observed in HCV patients compared with controls. Patients who cleared HCV after antiviral treatment showed a complete restoration of pPAF-AH activity and significant decrease of PAF levels during the follow-up. No data exist about the PAF/pPAF-AH system behaviour during HCV infection. This study shows that in HCV patients modifications of pPAF-AH activity/PAF levels take place and that HCV clearance restored pPAF-AH activity. This suggests that circulating viral particles play a role in PAF/pPAF-AH system modifications and such an alteration could be involved in HCV-related damage.

Association between a leukotriene C4 synthase gene promoter polymorphism and coronary artery calcium in young women: the Muscatine Study

OBJECTIVE

A majority of the recognized risk factors for atherosclerosis and the development of cardiovascular disease have been derived from the study of older populations who have already manifested clinical symptoms. If risk factors can be identified earlier in life, such as genetic variation, preventive measures may be taken before overt symptoms of pathology have manifested, and when treatments may be most effective.

METHODS AND RESULTS

In an effort to identify individuals at increased risk for cardiovascular disease, we genotyped 732 members of the Muscatine Study Longitudinal Adult Cohort for candidate genetic markers associated with several pathogenetic processes. We identified age-adjusted increased risks for coronary artery calcium (OR 4.29; 95% CI 1.78, 10.31) and increased mean carotid artery intimal-medial thickness associated with the (-444)A>C promoter polymorphism of Leukotriene C4 Synthase (LTC4S) in women. There were no similar associations in men.

CONCLUSIONS

LTC4S plays a key role in the process of inflammation as the rate limiting enzyme in the conversion of arachidonic acid to cysteinyl-leukotrienes, important mediators of inflammatory responses. The (-444)C variant upregulates LTC4S mRNA expression, increasing the synthesis of proinflammatory leukotrienes. Our results support genetic variation modifying inflammatory pathways as an important mechanism in the development of atherosclerosis.

Atherosclerosis and systemic lupus erythematosus

Large increases in mortality related to premature atherosclerosis with coronary artery disease have been reported in patients with systemic lupus erythematosus (SLE). The current pathogenic hypothesis for atherosclerosis involves not only the classic factors identified in the Framingham study, but also includes chronic inflammation, corticosteroid therapy, excess of traditional risk factors, autoantibodies, immune complexes (containing antibodies to phospholipids, to oxidized low-density lipoproteins, and to endothelial cells), and cytokine-producing activated T cells. Early risk factor intervention and effective control of inflammation should be incorporated into the management of SLE to protect against atherosclerosis.

Phosphodiesterase III Inhibition Affects Platelet-Monocyte Aggregate Formation Depending on the Axis of Stimulation

OBJECTIVE

The purpose of this study was to investigate the effect of the phosphodiesterase (PDE) type 3 inhibitor milrinone on the adhesion of platelets to monocytes in vitro.

DESIGN

Prospective study.

SETTING

University experimental laboratory.

PARTICIPANTS

Ten healthy volunteers.

INTERVENTIONS

Whole blood was incubated with 1, 10, or 100 micromol/L of milrinone. After stimulation with N-formyl-methionyl-leucyl-phenylalanine (FMLP) or adenosine-5-diphosphate (ADP), platelet-monocyte adhesion and CD11b, PSGL-1, GPIIb/IIIa, and P-selectin expression were measured by flow cytometry.

MEASUREMENTS AND RESULTS

The formation of platelet-monocyte conjugates after PDE3 inhibition depended on the type of stimulation. In unstimulated and FMLP-stimulated blood platelet monocytes, aggregation was enhanced by increasing concentrations of milrinone. This augmentation was accompanied by a rise in P-selectin expression in platelets. In ADP-stimulated blood the number of platelet-monocyte aggregates decreased with increasing concentrations of milrinone. Concurrent with the reported antiinflammatory properties of PDE-inhibition, an inhibition of CD11b expression was found in monocytes after stimulation with FMLP. In contrast, in unstimulated samples lower concentrations of milrinone caused an increase in CD11b.

CONCLUSIONS

These findings suggest that the effects of PDE3 inhibition on platelets and monocytes are modified by the type of stimulation and only partially suppress the inflammatory response of platelets and monocytes. The increase in platelet-monocyte conjugates in unstimulated and FMLP-stimulated blood suggested that PDE3 inhibition may also trigger proinflammatory reactions.

Platelet-activating factor increases VE-cadherin tyrosine phosphorylation in mouse endothelial cells and its association with the PtdIns3'-kinase

Platelet-activating factor (PAF), a potent inflammatory mediator, is involved in endothelial permeability. This study was designed to characterize PAF receptor (PAF-R) expression and its specific contribution to the modifications of adherens junctions in mouse endothelial cells. We demonstrated that PAF-R was expressed in mouse endothelial cells and was functionally active in stimulating p42/p44 MAPK and phosphatidylinositol 3-kinase (PtdIns3'-kinase)/Akt activities. Treatment of cells with PAF induced a rapid time- and dose-dependent (10(-7) to 10(-10) M) increase in tyrosine phosphorylation of a subset of proteins ranging from 90 to 220 kDa, including the VE-cadherin, the latter effect being prevented by the tyrosine kinase inhibitors herbimycin A and bis-tyrphostin. We demonstrated that PAF promoted formation of multimeric aggregates of VE-cadherin with PtdIns3'-kinase, which was also inhibited by herbimycin and bis-tyrphostin. Finally, we show by immunostaining of endothelial cells VE-cadherin that PAF dissociated adherens junctions. The present data provide the first evidence that treatment of endothelial cells with PAF promoted activation of tyrosine kinases and the VE-cadherin tyrosine phosphorylation and PtdIns3'-kinase association, which ultimately lead to the dissociation of adherens junctions. Physical association between PtdIns3'-kinase, serving as a docking protein, and VE-cadherin may thus provide an efficient mechanism for amplification and perpetuation of PAF-induced cellular activation.

Lipoprotein-associated phospholipase A2 as a biomarker for coronary disease and stroke

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), also known as platelet-activating factor acetylhydrolase, is a plasma enzyme that circulates bound to lipoproteins. The association between Lp-PLA(2) and atherosclerosis is ambiguous, as it can both degrade and generate potentially damaging vasoactive molecules. In this article, we speculate that Lp-PLA(2) associated with HDL might have cardioprotective properties, whereas the same enzyme bound to LDL might contribute directly to atherosclerosis at all stages, from lipoprotein oxidation to endothelial dysfunction, and plaque initiation and growth. Genetic and animal model studies give varying indications as to the contribution of Lp-PLA(2) to atherogenesis and tend to support the view that higher Lp-PLA(2) levels are cardioprotective. By contrast, a series of population studies point clearly to a positive association between plasma Lp-PLA(2) levels or activity levels and risk of coronary heart disease or stroke. Typically, people with Lp-PLA(2) levels in the highest quintile of the population have about a twofold greater risk than those in the lowest quintile. It is, perhaps, too early to introduce Lp-PLA(2) as a population-wide biomarker for coronary heart disease risk; however, with accumulating evidence, it might find a place in a stepwise risk assessment of individuals who require more aggressive intervention to prevent vascular disease.

Neutrophil Adherence to Bladder Microvascular Endothelial Cells following Platelet-Activating Factor Acetylhydrolase Inhibition

Interstitial cystitis (IC) is an inflammatory bladder condition of unknown etiology. Tryptase released from elevated numbers of activated mast cells is a proposed mediator of the inflammatory process in IC. We have previously shown that tryptase increases human bladder microvascular endothelial cell (HBMEC) calcium-independent phospholipase A(2) (iPLA(2)) activity, resulting in the production of multiple biologically active phospholipid metabolites, including platelet-activating factor (PAF), that can mediate inflammation. Because the design of selective PLA(2) inhibitors may provide a useful therapeutic strategy to reduce the inflammatory process in IC, we tested several frequently used PLA(2) inhibitors on PAF production in tryptase-stimulated HBMEC. Among the inhibitors tested, methyl arachidonyl fluorophosphonate (MAFP) was found to be a potent inhibitor of PAF-acetylhydrolase activity. Pretreatment of HBMEC with MAFP significantly increased PAF production in both unstimulated and tryptase-stimulated cells. In addition, MAFP pretreatment of tryptase-stimulated HBMEC increased both surface expression of P-selectin and polymorphonuclear leukocyte adherence to the HBMEC monolayer. These effects suggest that MAFP has a proinflammatory effect, irrespective of its ability to inhibit PLA(2).

Phospholipid mediators in the vessel wall: involvement in atherosclerosis

PURPOSE OF REVIEW

This review provides a brief update on the involvement of major phospholipid mediators, with the emphasis on platelet-activating factor and its analogues generated upon the oxidation of lipoproteins in vascular pathology, including atherogenesis.

RECENT FINDINGS

Phospholipid mediators are produced during inflammation by various enzymes, mostly from pre-existing membrane phospholipids, and trigger cellular signaling via G-coupled receptors. A short description of lysophosphatidic acid, lysophosphocholine and sphingosine-1 phosphate receptors and their actions is given, but attention is focused mainly on platelet-activating factor and its analogues. The majority of these mediators participate in leukocyte adhesiveness to the endothelium, leukocyte transmigration into the vessel wall and the subsequent formation of various chemokines leading to foam cell formation and smooth muscle cell proliferation and dedifferentiation. Platelet-activating factor and platelet-activating factor-like phospholipids are degraded in plasma by the lipoprotein-bound enzyme of myeloid origin, PAF-acetylhydrolase, also known as LDL-PLA2. Although the overexpression of PAF-acetylhydrolase shows marked anti-atherogenic properties in animal models, epidemiological data in the Caucasian population have demonstrated that its level might be a risk factor for cardiovascular disease. Recent genetic studies have shown, however, that the A379V polymorphism of this gene, responsible for slightly higher enzymatic activity, exerts a protective effect, probably by modifying the enzyme function towards a less atherogenic form.

SUMMARY

Phospholipid-borne mediators are certainly key players in inflammation and thus in atherosclerosis. The generation of such biologically active molecules is possibly dependent on nutritional habits and the availability of antioxidants, including enzymes protective against oxidative damage, including PAF-acetylhydrolase.

Inflammation in atherosclerosis and implications for therapy

Atherosclerosis is now understood to be a disease characterized by inflammation that results in a host of complications, including ischemia, acute coronary syndromes (unstable angina pectoris and myocardial infarction), and stroke. Inflammation may be caused by a response to oxidized low-density lipoproteins, chronic infection, or other factors; and markers of this process, such as C-reactive protein, may be useful to predict an increased risk of coronary heart disease. Thus, we believe that inflammatory processes may be potential targets of therapy in preventing or treating atherosclerosis and its complications.

Platelet-activating factor, a pleiotrophic mediator of physiological and pathological processes

Platelet-activating factor (PAF) is a potent proinflammatory phospholipid with diverse pathological and physiological effects. This bioactive phospholipid mediates processes as diverse as wound healing, physiological inflammation, apoptosis, angiogenesis, reproduction and long-term potentiation. Recent progress has demonstrated the participation of MAP kinase signaling pathways as modulators of the two critical enzymes, phospholipase A2 and acetyltransferase, involved in the remodeling pathway of PAF biosynthesis. The unregulated production of structural analogs of PAF by non-specific oxidative reactions has expanded this superfamily of signaling molecules to include "PAF-like" lipids whose mode of action is identical to that of authentic PAF. The action of members of this family is mediated by the PAF receptor, a G protein-coupled membrane-spanning molecule that can engage multiple signaling pathways in various cell types. Inappropriate activation of this signaling pathway is associated with many diseases in which inflammation is thought to be one of the underlying features. Inactivation of all members of the PAF superfamily occurs by a unique class of enzymes, the PAF acetylhydrolases, that have been characterized at the molecular level and that terminate signals initiated by both regulated and unregulated PAF production.

Vitamins in human arteriosclerosis with emphasis on vitamin C and vitamin E

INTRODUCTION

This review focuses on the process of arteriosclerosis arising from oxidative stress on lipoproteins and the general failure of randomized human trials using vitamins to retard this process.

REVIEW

As well as clinical trials, the paper reviews the mechanisms by which a variety of oxidants act. Antioxidants are discussed, emphasizing interactions of vitamins C and E with transition metals that can lead to prooxidation. There is a focus on interactions between supplemental or co-antioxidants that counterbalance prooxidant effects of one another.

CONCLUSIONS

It is concluded that normal cellular supplementation mechanisms are poorly accessible in the arteriosclerotic plaque leading to a prooxidant environment in which the haphazard introduction of vitamins could potentially be hazardous. Continued investigations into basic and clinical redox interactions of the kind discussed in this review using new measuring techniques may lead to approaches whereby antioxidants can be introduced into tissue in controlled ways for reducing arteriosclerosis.

Genetic determinants of arterial calcification associated with atherosclerosis

Increasing research interest has focused on arterial calcification in the setting of atherosclerosis. Many features of atherosclerosis-related calcification provide useful clinical information. For example, calcium mineral deposits frequently form in atherosclerotic plaque, and intimal arterial calcification can be used as a surrogate marker for atherosclerosis; also, calcium deposits are readily and noninvasively quantified, which is useful because greater amounts of coronary calcification predict a higher risk of myocardial infarction and death. Several mechanisms leading to calcification associated with atherosclerosis have been proposed; however, no direct testing of proposed mechanisms has yet been reported. Studies in genetically altered animals and in humans have shed light on potential genetic determinants, which in turn could form the basis for a more comprehensive understanding of the factors affecting calcification within plaque and the associated pathobiologic implications. We review proposed molecular and cellular mechanisms of atherosclerosis-associated arterial calcification, summarize genetic influences, and suggest areas in which further investigation is needed. Understanding the molecular and genetic determinants of specific structural plaque components such as calcification can provide a solid foundation for the development of novel therapeutic approaches to favorably alter plaque structure and minimize vulnerability to arterial rupture.

Arachidonate 5-lipoxygenase promoter genotype, dietary arachidonic acid, and atherosclerosis

BACKGROUND

Leukotrienes are inflammatory mediators generated from arachidonic acid (polyunsaturated n-6 fatty acid) by the enzyme 5-lipoxygenase. Since atherosclerosis involves arterial inflammation, we hypothesized that a polymorphism in the 5-lipoxygenase gene promoter could relate to atherosclerosis in humans and that this effect could interact with the dietary intake of competing 5-lipoxygenase substrates.

METHODS

We determined 5-lipoxygenase genotypes, carotid-artery intima-media thickness, and markers of inflammation in a randomly sampled cohort of 470 healthy, middle-aged women and men from the Los Angeles Atherosclerosis Study. Dietary arachidonic acid and marine n-3 fatty acids (including a competing 5-lipoxygenase substrate that reduces the production of inflammatory leukotrienes) were measured with the use of six 24-hour recalls of food intake.

RESULTS

Variant 5-lipoxygenase genotypes (lacking the common allele) were found in 6.0 percent of the cohort. Mean (+/-SE) intima-media thickness adjusted for age, sex, height, and racial or ethnic group was increased by 80+/-19 microm (95 percent confidence interval, 43 to 116; P<0.001) among carriers of two variant alleles, as compared with carriers of the common (wild-type) allele. In multivariate analysis, the increase in intima-media thickness among carriers of two variant alleles (62 microm, P<0.001) was similar in this cohort to that associated with diabetes (64 microm, P=0.01), the strongest common cardiovascular risk factor. Increased dietary arachidonic acid significantly enhanced the apparent atherogenic effect of genotype, whereas increased dietary intake of n-3 fatty acids blunted the effect. Finally, the plasma level of C-reactive protein, a marker of inflammation, was increased by a factor of 2 among carriers of two variant alleles as compared with that among carriers of the common allele.

CONCLUSIONS

Variant 5-lipoxygenase genotypes identify a subpopulation with increased atherosclerosis. The observed diet-gene interactions further suggest that dietary n-6 polyunsaturated fatty acids promote, whereas marine n-3 fatty acids inhibit, leukotriene-mediated inflammation that leads to atherosclerosis in this subpopulation.

GP IIb/IIIa inhibition with eptifibatide lowers levels of soluble CD40L and RANTES after percutaneous coronary intervention

Platelets are the most abundant blood source of CD40L, a proinflammatory and prothrombotic costimulatory molecule implicated in atherosclerosis. Agonist stimulation results in the secretion of a soluble form of CD40L (sCD40L) and GP IIb/IIIa receptor inhibition blocks secretion of sCD40L in vitro. However, the effect of GP IIb/IIIa inhibition on sCD40L levels in humans is unknown. Plasma sCD40L and inflammatory markers were measured (t = 0, 0.5, 2, and 24 hr post-PCI) in a cohort of patients receiving abciximab (n = 15), eptifibatide (n = 15), or no GP IIb/IIIa inhibitor (n = 15). PCI in the absence of GP IIb/IIIa inhibitor was associated with a small but measurable rise in sCD40L and the platelet-derived chemokine RANTES. In contrast, eptifibatide significantly lowered baseline sCD40L (P = 0.018) and RANTES (P = 0.006) levels. This effect was not observed with abciximab. GP IIb/IIIa inhibition with eptifibatide lowers levels of sCD40L and RANTES post-stenting, possibly conferring anti-inflammatory as well as antithrombotic effects.

Inhibition of Platelet-Activating Factor (PAF) Acetylhydrolase by Methyl Arachidonyl Fluorophosphonate Potentiates PAF Synthesis in Thrombin-Stimulated Human Coronary Artery Endothelial Cells

We have previously demonstrated that thrombin stimulation of endothelial cells results in increased membrane-associated, Ca(2+)-independent phospholipase A2 (iPLA2) activity, accelerated hydrolysis of membrane plasmalogen phospholipids, and production of several biologically active phospholipid metabolites, including prostacyclin and platelet-activating factor (PAF) that is abolished by pretreatment with the iPLA2-selective inhibitor bromoenol lactone. This study was designed to further investigate the role of alternative PLA2 inhibitors, including methyl arachidonyl fluorophosphonate (MAFP, an inhibitor of cytosolic PLA2 isoforms), on phospholipid turnover and PAF production from thrombin-stimulated human coronary artery endothelial cells (HCAECs). Paradoxically, pretreatment of HCAEC with MAFP (5-25 microM) resulted in a significant increase in PAF production in both unstimulated and thrombin-stimulated cells that was found to be a direct result of inhibition of PAF acetylhydrolase (PAF-AH) activity. Pretreatment with MAFP did not significantly inhibit HCAEC PLA2 activity, possibly due to the localization of PLA2 activity in the membrane fraction rather than the cytosol. Bromoenol lactone did not inhibit PAF-AH activity, even at concentrations as high as 20 microM. We conclude that MAFP augments thrombin-stimulated PAF production by inhibition of PAF catabolism without affecting membrane-associated iPLA2 activity.