Effect of lysophosphatidylcholine on vasomotor functions of porcine coronary arteries

Autotaxin-lysophosphatidic acid receptor 5 axis evokes endothelial dysfunction via reactive oxygen species signaling

Lysophosphatidylcholine (LPC) is a bioactive lipid that has been shown to attenuate endothelium-dependent vasorelaxation contributing to endothelial dysfunction; however, the underlying mechanisms are not well understood. In this study, we investigated the molecular mechanisms involved in the development of LPC-evoked impairment of endothelium-dependent vasorelaxation. In aortic rings isolated from wild-type (WT) mice, a 20-min exposure to LPC significantly reduced the acetylcholine chloride (ACh)-induced vasorelaxation indicating the impairment of normal endothelial function. Interestingly, pharmacological inhibition of autotaxin (ATX) by GLPG1690 partially reversed the endothelial dysfunction, suggesting that lysophosphatidic acid (LPA) derived from LPC may be involved in the effect. Therefore, the effect of LPC was also tested in aortic rings isolated from different LPA receptor knock-out (KO) mice. LPC evoked a marked reduction in ACh-dependent vasorelaxation in Lpar1, Lpar2, and Lpar4 KO, but its effect was significantly attenuated in Lpar5 KO vessels. Furthermore, addition of superoxide dismutase reduced the LPC-induced endothelial dysfunction in WT but not in the Lpar5 KO mice. In addition, LPC increased H2O2 release from WT vessels, which was significantly reduced in Lpar5 KO vessels. Our findings indicate that the ATX-LPA-LPA5 receptor axis is involved in the development of LPC-induced impairment of endothelium-dependent vasorelaxation via LPA5 receptor-mediated reactive oxygen species production. Taken together, in this study, we identified a new pathway contributing to the development of LPC-induced endothelial dysfunction.

Signalling by lysophosphatidate and its health implications

Extracellular lysophosphatidate (LPA) signalling is regulated by the balance of LPA formation by autotaxin (ATX) versus LPA degradation by lipid phosphate phosphatases (LPP) and by the relative expressions of six G-protein-coupled LPA receptors. These receptors increase cell proliferation, migration, survival and angiogenesis. Acute inflammation produced by tissue damage stimulates ATX production and LPA signalling as a component of wound healing. If inflammation does not resolve, LPA signalling becomes maladaptive in conditions including arthritis, neurologic pain, obesity and cancers. Furthermore, LPA signalling through LPA1 receptors promotes fibrosis in skin, liver, kidneys and lungs. LPA also promotes the spread of tumours to other organs (metastasis) and the pro-survival properties of LPA explain why LPA counteracts the effects of chemotherapeutic agents and radiotherapy. ATX is secreted in response to radiation-induced DNA damage during cancer treatments and this together with increased LPA1 receptor expression leads to radiation-induced fibrosis. The anti-inflammatory agent, dexamethasone, decreases levels of inflammatory cytokines/chemokines. This is linked to a coordinated decrease in the production of ATX and LPA1/2 receptors and increased LPA degradation through LPP1. These effects explain why dexamethasone attenuates radiation-induced fibrosis. Increased LPA signalling is also associated with cardiovascular disease including atherosclerosis and deranged LPA signalling is associated with pregnancy complications including preeclampsia and intrahepatic cholestasis of pregnancy. LPA contributes to chronic inflammation because it stimulates the secretion of inflammatory cytokines/chemokines, which increase further ATX production and LPA signalling. Attenuating maladaptive LPA signalling provides a novel means of treating inflammatory diseases that underlie so many important medical conditions.

GPR55 agonist lysophosphatidylinositol and lysophosphatidylcholine inhibit endothelial cell hyperpolarization via GPR-independent suppression of Na+-Ca2+ exchanger and endoplasmic reticulum Ca2+ refilling

Lysophosphatidylinositol (LPI) and lysophosphatidylcholine (LPC) are lipid signaling molecules that induce endothelium-dependent vasodilation. In addition, LPC suppresses acetylcholine (Ach)-induced responses. We aimed to determine the influence of LPC and LPI on hyperpolarizing responses in vitro and in situ endothelial cells (EC) and identify the underlying mechanisms. Using patch-clamp method, we show that LPI and LPC inhibit EC hyperpolarization to histamine and suppress Na⁺/Ca²⁺ exchanged (NCX) currents in a concentration-dependent manner. The inhibition is non-mode-specific and unaffected by intracellular GDPβS infusion and tempol, a superoxide dismutase mimetic. In excised mouse aorta, LPI strongly inhibits the sustained and the peak endothelial hyperpolarization induced by Ach, but not by SKA-31, an opener of Ca²⁺-dependent K⁺ channels of intermediate and small conductance. The hyperpolarizing responses to consecutive histamine applications are strongly reduced by NCX inhibition. In a Ca²⁺-re-addition protocol, bepridil, a NCX inhibitor, and KB-R7943, a blocker of reversed NCX, inhibit the hyperpolarizing responses to Ca²⁺-re-addition following Ca²⁺ stores depletion. These finding indicate that LPC and LPI inhibit endothelial hyperpolarization to Ach and histamine independently of G-protein coupled receptors and superoxide anions. Reversed NCX is critical for ER Ca²⁺ refilling in EC. The inhibition of NCX by LPI and LPC underlies diminished endothelium-dependent responses and endothelial dysfunction accompanied by increased levels of these lipids in the blood.

Soluble guanylate cyclase redox state under oxidative stress conditions in isolated monkey coronary arteries

Coronary artery disease is associated with oxidative stress due to the excessive generation of free radicals in the vascular wall. This study investigated the impact of tert‐butyl hydroperoxide (t‐BuOOH), a peroxyl radical generator, on the redox state of soluble guanylate cyclase (sGC) in isolated monkey coronary arteries. Helically cut strips of endothelium‐intact monkey coronary arteries treated with the nitric oxide synthase inhibitor N^G‐nitro‐L‐arginine (10 μmol/L) were exposed for approximately 60 min to either no drug or t‐BuOOH (100 μmol/L) in the presence and absence of α‐tocopherol (300 μmol/L). Relaxation and cGMP levels in response to the sGC stimulator BAY 41‐2272 and the sGC activator BAY 60‐2770 were assessed by organ chamber technique and enzyme immunoassay, respectively. The relaxant response to BAY 41‐2272 was significantly impaired by the exposure to t‐BuOOH, whereas the response to BAY 60‐2770 was significantly augmented. In addition, vascular cGMP accumulation caused by BAY 41‐2272 was decreased by the exposure to t‐BuOOH, whereas for BAY 60‐2770, it was increased. These effects of t‐BuOOH were abolished by coincubation with α‐tocopherol. Furthermore, correlations were observed between BAY compound‐induced relaxant magnitudes and cGMP levels. Therefore, it is concluded that increased oxidative stress leads to disruption of the sGC redox state in monkey coronary arteries. This finding is of great importance for understanding coronary physiology in primates.

Lipoprotein-associated phospholipase A2 levels are associated with erectile dysfunction in patients without known coronary artery disease

Endothelial dysfunction and microvascular damage play a crucial role in the pathogenesis of erectile dysfunction (ED). Lp-PLA2 is a calcium-independent member of the phospholipase A2 family and hydrolyses oxidised phospholipids on low-density lipoprotein (LDL) particles that plays a pivotal role in ox-LDL-induced endothelial dysfunction. The purpose of the current study was to determine the association between Lp-PLA2 levels and ED in patients without known coronary artery disease (CAD). All patients were evaluated for ED and divided into two groups: 88 patients suffering from ED for >1 year were enrolled as an experimental group and 88 patients without ED were enrolled as a control group in this study. Diagnosis of ED was based on the International Index of Erectile Function Score-5. Levels of Lp-PLA2 were measured in serum by colorimetric assay. The relationship between Lp-PLA2 levels and ED in patients was evaluated statistically. The mean age of patients with ED group was 59.4 ± 11.32 and 55.8 ± 9.67 in the control group. Plasma Lp-PLA2 levels were significantly higher in ED than in the control group (220.3 ± 66.90 and 174.8 ± 58.83 pg ml(-1) , respectively, P < 0.001). The Lp-PLA2 levels were negatively correlated with score of ED (r = -0.482, P < 0.05). In logistic regression analysis, enhanced plasma Lp-PLA2 levels result in approximately 1.2-fold increase in ED [1.22 (1.25-2.76)]. In this study, serum Lp-PLA2 levels were found to be associated with endothelial dysfunction predictive of ED. Serum Lp-PLA2 level appears to be a specific predictor of ED, and it may be used in early prediction of ED in the male population.

Lipoprotein-associated phospholipase A2 activity predicts cardiovascular events in high risk coronary artery disease patients

Objective

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is deemed to play a role in atherosclerosis and plaque destabilization as demonstrated in animal models and in prospective clinical studies. However, most of the literature is either focused on high-risk, apparently healthy patients, or is based on cross sectional studies. Therefore, we tested the hypothesis that serum Lp-PLA2 mass and activity are useful for predicting cardiovascular (CV) events over the coronary atherosclerotic burden and conventional risk factors in high-risk coronary artery disease patients.

Methods and Results

In a prospective cohort study of 712 Caucasian patients, who underwent coronary angiography and measurement of both Lp-PLA2 mass and activity at baseline, we determined incident CV events at follow-up after splitting the patients into a high and a low Lp-PLA2 mass and activity groups based on ROC analysis and Youden index. Kaplan-Meier and propensity score matching analysis were used to compare CV event-free survival between groups. Follow-up data were obtained in 75% of the cohort after a median of 7.2 years (range 1–12.7 years) during which 129 (25.5%) CV events were observed. The high Lp-PLA2 activity patients showed worse CV event-free survival (66.7% vs. 79.5%, p = 0.023) and acute coronary syndrome-free survival (75.4% vs. 85.6%, p = 0.04) than those in low Lp-PLA2 group.

Conclusions

A high Lp-PLA2 activity implies a worse CV prognosis at long term follow up in high-risk Caucasian patients referred for coronary angiography.

Lipoprotein-Associated Phospholipase A2

The role of inflammation in atherosclerosis continues to emerge. Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), a novel plasma biomarker, circulates in the blood bound mainly to low-density lipoprotein (LDL) and promotes vascular inflammation. Several epidemiological studies have shown that circulating levels of Lp-PLA(2) are an independent risk factor for cardiovascular events. Recent studies demonstrate that Lp-PLA(2) is also associated with endothelial dysfunction and early atherosclerosis. This review provides an overview of these studies, suggests plausible mechanisms for the association between endothelial dysfunction and Lp-PLA(2), and highlights future potential therapies.

Lipoprotein associated phospholipase A(2): role in atherosclerosis and utility as a biomarker for cardiovascular risk

Atherosclerosis and its clinical manifestations are widely prevalent throughout the world. Atherogenesis is highly complex and modulated by numerous genetic and environmental risk factors. A large body of basic scientific and clinical research supports the conclusion that inflammation plays a significant role in atherogenesis along the entire continuum of its progression. Inflammation adversely impacts intravascular lipid handling and metabolism, resulting in the development of macrophage foam cell, fatty streak, and atheromatous plaque formation. Given the enormous human and economic cost of myocardial infarction, ischemic stroke, peripheral arterial disease and amputation, and premature death and disability, considerable effort is being committed to refining our ability to correctly identify patients at heightened risk for atherosclerotic vascular disease and acute cardiovascular events so that they can be treated earlier and more aggressively. Serum markers of inflammation have emerged as an important component of risk factor burden. Lipoprotein-associated phospholipase A2 (Lp-PLA(2)) potentiates intravascular inflammation and atherosclerosis. A variety of epidemiologic studies support the utility of Lp-PLA(2) measurements for estimating and further refining cardiovascular disease risk. Drug therapies to inhibit Lp-PLA(2) are in development and show considerable promise, including darapladib, a specific molecular inhibitor of the enzyme. In addition to substantially inhibiting Lp-PLA(2) activity, darapladib reduces progression of the necrotic core volume of human coronary artery atheromatous plaque. The growing body of evidence points to an important role and utility for Lp-PLA(2) testing in preventive and personalized clinical medicine.

Lysophosphatidylcholine induces endothelial cell injury by nitric oxide production through oxidative stress

OBJECTIVE

To determine whether lysophosphatidylcholine (LPC) induces endothelial cell injury by altering the production of nitric oxide (NO) and thereby increasing reactive oxygen species (ROS).

METHODS

Human umbilical vein endothelial cells (HUVECs) were cultured and exposed to LPC, LPC with N(G)-nitro-l-arginine methyl ester (L-NAME), LPC with antioxidants. LPC-induced cell injury and viability were determined using LDH and Resazurin assays. The Mann-Whitney U test was used for statistical analysis.

RESULTS

LPC induced HUVEC injury in a concentration-dependent manner. LPC induced the overproduction of NO and ROS in HUVECs and LPC-induced HUVEC injury is significantly inhibited by the eNOS inhibitor (L-NAME) and the antioxidants (p < 0.05).

CONCLUSIONS

These findings suggest that LPC induces the overproduction of NO, which may increase the oxidative stress on endothelial cells and lead to endothelial cell injury.

Lactosylceramide promotes cell migration and proliferation through activation of ERK1/2 in human aortic smooth muscle cells

Increased plasma levels of lactosylceramide (LacCer) have been associated with cardiovascular disease. However, it is largely unknown whether LacCer directly contributes to dysfunction of smooth muscle cells (SMCs), a key event in vascular lesion formation. In the present study, we determined the effects and potential mechanisms of LacCer on cell migration and proliferation in human aortic SMCs (AoSMCs). Cell migration and proliferation were determined by a modified Boyden chamber assay and nonradioactive colorimetric (MTS) assay, respectively. We found that LacCer significantly induced AoSMC migration and proliferation in a concentration- and time-dependent manner. In addition, LacCer significantly upregulated the expression of PDGFR-B, integrins (alpha(v) and beta(3)), and matrix metalloproteinases (matrix metalloproteinase-1 and -2) at both mRNA and protein levels, as determined by real-time PCR and Western blot analyses, respectively. Furthermore, LacCer increased superoxide anion production and the transient phosphorylation of ERK1/2 in AoSMCs, as determined by dihydroethidium staining and immunoassay, respectively. Accordingly, LacCer-induced cell migration and proliferation were effectively blocked by antioxidants (seleno-l-methionine and Mn tetrakis porphyrin) and by a specific ERK1/2 inhibitor. Thus, LacCer promotes cell migration and proliferation through oxidative stress and activation of ERK1/2 in AoSMCs. These findings demonstrate the functional role of LacCer in the vascular disease pathogenesis.

Chlamydia heat shock protein 60 decreases expression of endothelial nitric oxide synthase in human and porcine coronary artery endothelial cells

AIMS

Clinically, Chlamydia pneumoniae infection and its heat shock protein 60 (cHSP60) may contribute to atherogenesis; however, its underlying mechanisms are largely unknown. The objective of this study was to determine whether cHSP60 could cause endothelial dysfunction in human coronary artery endothelial cells (HCAECs) and porcine coronary arteries.

METHODS AND RESULTS

When HCAECs were treated with recombinant cHSP60, endothelial nitric oxide synthase (eNOS) mRNA and protein levels, enzyme activities, cellular NO levels, mRNA stability, and promoter activities were significantly decreased. Superoxide anion production was significantly increased due to the inhibition of mitochondrial membrane potential and catalase and superoxide dismutase (SOD) activities as well as activation of NADPH oxidase. Antioxidant seleno-l-methionine (SeMet) or SOD mimetic MnTBAP effectively blocked cHSP60-induced eNOS downregulation. In addition, cHSP60 activated mitogen-activated protein kinases (MAPKs) including p38, c-Jun-N-terminal kinase/stress-activated protein kinase, and extracellular signal-regulated kinases. Specific chemical inhibitors or their dominant-negative mutant forms of these MAPKs effectively blocked cHSP60-induced eNOS downregulation. cHSP60-induced eNOS downregulation and oxidative stress were also demonstrated in porcine coronary artery rings in vitro. Functionally, endothelium-dependent vasorelaxation was significantly reduced in cHSP60-treated vessels.

CONCLUSION

cHSP60 directly induces eNOS downregulation through oxidative stress and MAPK activation in both HCAECs and porcine coronary arteries, thereby causing endothelial dysfunction.

Lipoprotein-associated phospholipase A2: a cardiovascular risk predictor and a potential therapeutic target

Lipoprotein-associated phospholipase A2 (Lp-PLA2), present in the circulation and in atherosclerotic plaque, is an inflammatory marker with potential use as a predictor of cardiovascular risk and as a therapeutic target. Although Lp-PLA2 is associated with both LDL and HDL, it is important to determine whether Lp-PLA2 has a predominantly pro- or anti-atherogenic effect. Increasing evidence suggests a proatherogenic role for Lp-PLA2. ©iEpidemiologic and clinical evidence suggests Lp-PLA2 is an independent predictor of risk and may be superior to other inflammatory markers owing to its specificity and minimal biovariation. Lp-PLA2 inhibitors currently being investigated in clinical trials are promising novel anti-inflammatory agents with a specificity for the vascular bed and a potential for decreasing plaque vulnerability.

Protective effects of EPA and deleterious effects of DHA on eNOS activity in Ea hy 926 cultured with lysophosphatidylcholine

Oxidized low density lipoprotein (Ox-LDL) is a well-established risk factor in atherosclerosis and lysophosphatidylcholine (LysoPtdCho) is considered to be one of the major atherogenic component of Ox-LDL. The purpose of this work was to investigate the effects of two membrane n-3 long chain polyunsaturated fatty acids (n-3 PUFAs), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) compared to n-6 PUFA, ARA (arachidonic acid), on the activation of endothelial NO synthase (eNOS) by histamine in Ea hy 926 endothelial cells incubated during 24 h in the presence or the absence of LysoPtdCho. DHA (50 muM) produced a ROS induction in cells and aggravated the LysoPtdCho-induced oxidative stress. It did not modify the basal eNOS activity but impaired the stimulation of eNOS induced by histamine and was unable to correct the deleterious effect of LysoPtdCho on histamine-stimulated eNOS activity or phosphorylation of Ser 1177. In contrast, EPA (90 muM) did not modify the ROS level produced in the presence or absence of LysoPtdCho or basal eNOS activity and the stimulating effect of histamine on eNOS. However, it diminished the deleterious effect of LysoPtdCho as well as on the histamine-stimulated eNOS activity on the phosphorylation on Ser 1177 of eNOS. The beneficial effect of EPA but not DHA on endothelial eNOS activity in Ea hy 926 could be also partially due to a slight decrease in membrane DHA content in EPA-treated cells. Consequently, the equilibrium between NO generated by eNOS and ROS due to oxidative stress could explain, in part, the beneficial effect of EPA on the development of cardiovascular diseases. By contrast ARA an n-6 PUFA was devoid of any effect on ROS generation or eNOS activity in the basal state or after histamine-induced stimulation. In vivo experiments should be undertaken to confirm these results.

Soluble CD40 ligand induces endothelial dysfunction in human and porcine coronary artery endothelial cells

The purpose of this study was to determine the effects and mechanisms of sCD40L on endothelial dysfunction in both human coronary artery endothelial cells (HCAECs) and porcine coronary artery rings. HCAECs treated with sCD40L showed significant reductions of endothelial nitric oxide synthase (eNOS) mRNA and protein levels, eNOS mRNA stability, eNOS enzyme activity, and cellular NO levels, whereas superoxide anion (O(2)(-)) production was significantly increased. sCD40L enhanced eNOS mRNA 3'UTR binding to cytoplasmic molecules and induced a unique expression pattern of 95 microRNAs. sCD40L significantly decreased mitochondrial membrane potential, and catalase and SOD activities, whereas it increased NADPH oxidase (NOX) activity. sCD40L increased phosphorylation of MAPKs p38 and ERK1/2 as well as IkappaBalpha and enhanced NF-kappaB nuclear translocation. In porcine coronary arteries, sCD40L significantly decreased endothelium-dependent vasorelaxation and eNOS mRNA levels, whereas it increased O(2)(-) levels. Antioxidant seleno-l-methionine; chemical inhibitors of p38, ERK1/2, and mitochondrial complex II; as well as dominant negative mutant forms of IkappaBalpha and NOX4 effectively blocked sCD40L-induced eNOS down-regulation in HCAECs. Thus, sCD40L reduces eNOS levels, whereas it increases oxidative stress through the unique molecular mechanisms involving eNOS mRNA stability, 3'UTR-binding molecules, microRNAs, mitochondrial function, ROS-related enzymes, p38, ERK1/2, and NF-kappaB signal pathways in endothelial cells.

Lysophosphatidylcholine up-regulates human endothelial nitric oxide synthase gene transactivity by c-Jun N-terminal kinase signalling pathway

Human endothelial nitric oxide synthase (eNOS) plays a pivotal role in maintaining blood pressure homeostasis and vascular integrity. It has recently been reported that mitogen-activated protein kinases (MAPKs) are intimately implicated in expression of eNOS. However detailed mechanism mediated by them remains to be clarified. In this study, eNOS gene transactivity in human umbilical vein endothelial cells was up-regulated by stimulation of lysophosphatidylcholine (LPC). The stimulation of LPC highly activated both extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK), with differences in the dynamic processes of activation between them. Unexpectedly, p38 MAPK could not be activated by the stimulation of LPC. The activation of JNK signalling pathway by overexpression of JNK or its upstream kinase active mutant up-regulated the transactivity of eNOS significantly, but the activation of p38 signalling pathway down-regulated it largely. The inhibition of either ERK1/2 or JNK signalling pathway by kinase-selective inhibitors could markedly block the induction of the transactivity by LPC. It was observed by electrophoretic mobility shift assay that LPC stimulated both SP1 and AP1 DNA binding activity to go up. Additionally using decoy oligonucleotides proved that SP1 was necessary for maintaining the basal or stimulated transactivity, whereas AP1 contributed mainly to the increase of the stimulated transactivity. These findings indicate that the up-regulation of the eNOS gene transactivity by LPC involves the enhancement of SP1 transcription factor by the activation of JNK and ERK1/2 signalling pathways and AP1 transcription factor by the activation of JNK signalling pathway.

Lipoprotein-associated phospholipase A2: a risk marker or a risk factor?

Multiple cardiovascular biomarkers are associated with increased cardiovascular disease (CVD) risk. Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) appears to be relatively unique in its high specificity for and the causal pathway of plaque inflammation. In both primary and secondary prevention study populations, Lp-PLA(2) was consistently associated with higher cardiovascular risk, and the risk estimate appears to be relatively unaffected by adjustment for conventional CVD risk factors. Risk ratios were similar, whether the mass concentration or activity of the enzyme was measured. The purpose of this article is to review the evidence for the clinical utility of Lp-PLA(2), both as a risk marker and as a risk factor involved in the causal pathway of plaque inflammation and the formation of rupture-prone plaque.

Neutrophil antimicrobial peptide alpha-defensin causes endothelial dysfunction in porcine coronary arteries

BACKGROUND

Defensins are cysteine-rich cationic polypeptides released from neutrophils that exhibit powerful antimicrobial activities. Because inflammation, including neutrophil infiltration and release of defensins, may play an important role in atherosclerosis and other vascular diseases, we determined whether alpha-defensin could cause endothelial dysfunction, a major initial event of atherosclerosis, in porcine coronary arteries.

METHODS

Porcine coronary arteries were sliced into 5-mm rings and treated with different concentrations of human recombinant alpha-defensin for 24 hours. Vasomotor reactivity was studied by using a myograph system. Levels of superoxide anion were detected by the lucigenin-enhanced chemiluminescence method. Endothelial nitric oxide synthase (eNOS) messenger RNA (mRNA) and protein levels were determined by real-time polymerase chain reaction and immunohistochemistry analysis, respectively.

RESULTS

Endothelium-dependent relaxation in response to bradykinin was significantly reduced by 40% for the rings treated with 1500 nM of alpha-defensin compared with controls (P< .05). Vessel contractility in response to the thromboxane A2 analogue U46619 and endothelium-independent relaxation in response to sodium nitroprusside were not affected with defensin treatment. In addition, the superoxide anion level at the endothelial layer of porcine coronary artery rings was significantly increased by 80% in the defensin-treated (1500 nM) vessels compared with controls (P< .05). Furthermore, the eNOS mRNA levels in endothelial cells isolated from the cultured rings treated with defensin (1500 nM) were significantly decreased by 27% compared with controls (P< .05). Immunoreactivity of eNOS in the defensin-treated vessel rings was also substantially reduced.

CONCLUSIONS

Defensin reduces the endothelium-dependent vasorelaxation. This effect is associated with increased superoxide radical production and decreased eNOS expression in porcine coronary arteries.

CLINICAL RELEVANCE

Inflammation is an important mechanism of atherosclerosis and other vascular diseases. The roles and interactions of biomediators released from inflammatory cells are not fully understood, however. This study provides new information about effects and potential molecular mechanisms of a major neutrophil releasing factor, alpha-defensin, on endothelial dysfunction of porcine coronary arteries. Thus, targeting alpha-defensin and its associated molecular mechanisms may become a new strategy to prevent vascular diseases.

Local Production of Lipoprotein-Associated Phospholipase A 2 and Lysophosphatidylcholine in the Coronary Circulation

Background— Lipoprotein-associated phospholipase A 2 (Lp-PLA 2 ) is a novel marker and participant in vascular inflammation. Inflammation also is associated with coronary atherosclerosis. We tested the hypothesis that local coronary production of Lp-PLA 2 is enhanced in patients with early coronary atherosclerosis and associated with local endothelial function.

Methods and Results— Coronary angiography, blood flow, flow reserve, endothelial function assessment, and intravascular ultrasound with volumetric analysis were performed in 15 patients with mild coronary atherosclerosis and in 15 control subjects. Plasma samples were collected simultaneously from the left main coronary artery and coronary sinus for measurement of Lp-PLA 2 , lysophosphatidylcholine (a product of Lp-PLA 2 ), and C-reactive protein. Hemodynamic parameters and cholesterol were similar in both groups. Arterial Lp-PLA 2 levels were similar in patients and control subjects: 225 ng/mL (interquartile range [IQR], 196 to 273 ng/mL) versus 221 ng/mL (IQR, 177 to 294 ng/mL). Lp-PLA 2 net production in the coronary circulation was higher in patients compared with control subjects: 519 ng/min (IQR, 198 to 1276 ng/min) versus −529 ng/min (IQR, −872 to −79 ng/min; P =0.001) and correlated with percent atheroma volume ( r s =0.37, P =0.04). Net production of lysophosphatidylcholine was higher in patients compared with control subjects: 199 ng/min (IQR, −592 to 470 ng/min) versus −505 ng/min (IQR, −1119 to 0 ng/min; P =0.03) and correlated with coronary endothelial dysfunction ( r s =0.5, P =0.005). C-reactive protein was not significantly different between the groups.

Conclusions— Early coronary atherosclerosis in humans is characterized by local production of Lp-PLA 2 . Local coronary production of lysophosphatidylcholine, the active product of Lp-PLA 2 , is associated with endothelial dysfunction. These results support the role for Lp-PLA 2 in the mechanism of regional vascular inflammation and atherosclerosis in humans.

Early experimental obesity is associated with coronary endothelial dysfunction and oxidative stress

Obesity is independently associated with increased cardiovascular risk. However, since established obesity clusters with various cardiovascular risk factors, configuring the metabolic syndrome, the early effects of obesity on vascular function are still poorly understood. The current study was designed to evaluate the effect of early obesity on coronary endothelial function in a new animal model of swine obesity. As to method, juvenile domestic crossbred pigs were randomized to either high-fat/high-calorie diet (HF) or normal chow diet for 12 wk. Coronary microvascular permeability and abdominal wall fat were determined by using electron beam computerized tomography. Epicardial endothelial function and oxidative stress were measured in vitro. Systemic oxidative stress, renin-angiotensin activity, leptin levels, and parameters of insulin sensitivity were evaluated. As a result, HF pigs were characterized by abdominal obesity, hypertension, and elevated plasma lysophosphatidylcholine and leptin in the presence of increased insulin sensitivity. Coronary endothelium-dependent vasorelaxation was reduced in HF pigs and myocardial microvascular permeability increased compared with those values in normal pigs. Systemic redox status in HF pigs was similar to that in normal pigs, whereas the coronary endothelium demonstrated higher content of superoxide anions, nitrotyrosine, and NADPH-oxidase subunits, indicating increased tissue oxidative stress. In conclusion, the current study shows that early obesity is characterized by increased vascular oxidative stress and endothelial dysfunction in association with increased levels of leptin and before the development of insulin resistance and systemic oxidative stress. Vascular dysfunction is therefore an early manifestation of obesity and might contribute to the increased cardiovascular risk, independently of insulin resistance.

CD40 ligand increases expression of its receptor CD40 in human coronary artery endothelial cells

BACKGROUND

Recently, CD40 ligand (CD40L) and its receptor CD40 have been implicated in atherosclerosis. Clinical data showed that elevated CD40L levels are associated with a high risk of cardiovascular events. The aim of this study was to investigate whether CD40L could affect the expression of its membrane receptor CD40 as a feedback mechanism by which CD40L could enhance its functions in human coronary artery endothelial cells (HCAECs).

METHODS

The HCAECs were treated with human soluble CD40L, and the messenger RNA (mRNA) and protein levels of CD40 were determined by real-time polymerase chain reaction and Western blot analysis, respectively. The specific effect of CD40L was confirmed by a blocking experiment with antibody against CD40L. Involvements of oxidative stress and mitogen-activated protein kinases (MAPKs) were also studied with antioxidant seleno-L-methionine (SeMet) and MAPK inhibitors such as extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor.

RESULTS

When HCAECs were cultured with CD40L (5 microg/mL) for 24 hours, CD40 mRNA levels were increased by 79% compared with controls (P < .05). Similarly, Western blot analysis showed an 80% increase in CD40 protein levels (P < .05). The CD40L-induced increase in CD40 mRNA levels were blocked specifically by anti-CD40L antibody. Antioxidant SeMet and specific ERK1/2 inhibitor (PD98059) also effectively blocked CD40L-induced CD40 mRNA increase.

CONCLUSIONS

These data demonstrate that clinically relevant concentration of CD40L increased the expression of its receptor CD40 in HCAECs. The CD40L-induced upregulation of CD40 may be mediated by oxidative stress and ERK1/2 activation. This study suggests a new mechanism by which CD40L could enhance its biologic functions in the vascular system and contribute to endothelial dysfunction and vascular disease.

Different expressions of Nogo-B1 and Nogo-B2 in mouse heart microvascular endothelial cell dysfunction induced by lysophosphatidylcholine

To investigate Nogo-B expression changes in mouse heart microvascular endothelial H5V cell line induced by lysophosphatidylcholine. Cells were incubated with different concentrations of lysoPC for the same incubation time and with 10 micromol/l lysoPC at different incubation times. Protein and mRNA expression levels of Nogo-B1 and Nogo-B2 were measured with Western blotting and semiquantitative RT-PCR, respectively. Nogo-B1 protein was detected in normal H5V cells by Western blotting. When H5V cells were incubated with lysoPC, Nogo-B1 protein level decreased, and the lowest point fell to 20% of the original level induced by 20 micromol/l lysoPC for 24 h. Incubation of H5V cells with lysoPC of different concentrations or at different time points caused little change in Nogo-B1 mRNA expression level, except for a 50% decrease in 20 micromol/l lysoPC at 24 h, while a transient change was observed in Nogo-B2 mRNA level. These results demonstrate that Nogo-B1 protein expression could be down-regulated with increasing concentrations of lysoPC and lapse of incubation time, though no mRNA transcription down-regulation occurred. However, mRNA expression level of Nogo-B2 showed a transient up-regulation induced by lysoPC. We conclude that the two subtypes of Nogo-B may play different roles in the endothelial cell injury process.

Specific impairment of endothelium-derived hyperpolarizing factor-type relaxation in mesenteric arteries from streptozotocin-induced diabetic mice

We hypothesized that the contribution made by endothelium-derived hyperpolarizing factor (EDHF) to acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR) might be altered in mesenteric arteries from streptozotocin (STZ)-induced diabetic mice. In endothelium-intact preparations, the ACh-induced EDR (but not the sodium nitroprusside-induced relaxation) was weaker in the STZ group than in age-matched controls. Indomethacin (10 muM) had no significant effect on EDR in either group, indicating that cyclooxygenase products, including prostacyclin, are not involved. This indomethacin-resistant EDR was weaker in the STZ group than in the controls. To isolate the EDHF-resistant component of EDR, charybdotoxin (100 nM) and apamin (100 nM) were present in the bath solution throughout the next experiment. This EDHF-resistant relaxation did not differ significantly between the two groups. On the other hand, the EDHF-mediated relaxation was significantly weaker in the STZ group than in the controls, and it was completely blocked by lysophosphatidylcholine (LPC, 10 microM) in each group. The eNOS protein expression was similar between the two groups. These results suggest that (a) the endothelial dysfunction present in mesenteric arteries from type 1 diabetic mice is largely attributable to reduced EDHF signaling, and (b) LPC may be involved in this attenuation of EDHF-mediated relaxation.