Oxidized low density lipoproteins induce mRNA expression and release of endothelin from human and porcine endothelium

Experiments were designed to examine the effect of oxidized low density lipoproteins (Ox-LDLs) on the expression and the release of endothelin from cultured endothelial cells and intact blood vessels. Ox-LDLs (30-300 micrograms/ml), but not native low density lipoproteins (200 micrograms/ml), stimulated the expression of preproendothelin mRNA in porcine and human endothelial cells, leading to a time- and concentration-dependent release of the peptide into the culture medium. The Ox-LDL-stimulated release of endothelin was mimicked by acetylated low density lipoprotein and abolished by downregulation of protein kinase C by phorbol ester. In the intact porcine aorta, Ox-LDLs, but not native low density lipoproteins, also increased the release of peptide in an endothelium- and concentration-dependent manner. The maximal effect was observed at a concentration of 100 micrograms/ml. Incubation of the intact porcine aorta with the scavenger receptor antagonist dextran sulfate decreased the formation of endothelium evoked by Ox-LDLs. The Ox-LDL-stimulated production of the peptide was further augmented in the presence of thrombin (4 units/ml) and was unaffected by nitric oxide-generating compound 3-morpholinosydnonimine (10(-5) M). These results suggest that Ox-LDL may be an endogenous mediator of the augmented release of endothelin observed in hyperlipidemia and atherosclerosis. The increased production of the peptide could contribute to vasospastic events and may promote vascular smooth muscle proliferation and progression of atherosclerotic vascular disease.

Oxidized low density lipoproteins inhibit relaxations of porcine coronary arteries. Role of scavenger receptor and endothelium-derived nitric oxide

BACKGROUND

We studied the effects of low density lipoprotein (LDL) on endothelium function.

METHODS AND RESULTS

Porcine epicardial and intramyocardial coronary arteries suspended in organ chambers for isometric tension recording were exposed to LDL for 2 hours and were then washed. In epicardial coronary arteries, oxidized LDL (30-300 micrograms/ml) but not native LDL or lysolecithin inhibited endothelium-dependent relaxations to serotonin, thrombin, and aggregating platelets (5,000-75,000/microliter). Endothelium-dependent relaxations to bradykinin and A23187 and endothelium-independent relaxations to SIN-1 were unaffected by oxidized LDL. In intramyocardial coronary arteries, oxidized LDL had no appreciable effect on relaxations to serotonin. The effect of oxidized LDL on the response to serotonin in epicardial coronary arteries was completely prevented by dextran sulfate (10 micrograms/ml). The inhibitory effect of oxidized LDL persisted in the presence of pertussis toxin. Similar to the lipoproteins, L-NG-monomethyl arginine (L-NMMA) reduced relaxations to serotonin but not to bradykinin in epicardial coronary arteries. In the presence of L-NMMA, oxidized LDL further reduced the response to serotonin. In arteries in which relaxations to serotonin were inhibited by oxidized LDL, L-arginine but not D-arginine induced a full relaxation. Pretreatment with L-arginine potentiated relaxations to serotonin in arteries exposed to oxidized LDL.

CONCLUSIONS

Thus, oxidized LDL activates the scavenger receptor on endothelial cells and inhibits the receptor-operated nitric oxide formation in epicardial but not in intramyocardial coronary arteries. The mechanism is not related to dysfunction of a Gi protein but is related to a reduced intracellular availability of L-arginine. The reduced nitric oxide formation at sites of early atherosclerotic lesions may favor platelet aggregation and vasospasm, both of which are known clinical events in patients with coronary artery disease.

Endothelial dysfunction in coronary artery disease

The endothelium is a physical barrier between the blood and vascular smooth muscle, a source of enzymes activating and deactivating cardiovascular hormones and a site of production of relaxing and contracting factors. In addition, the endothelium is a source of growth inhibitors and promoters of vascular smooth muscle cells. Monoaminooxidase deactivates catecholamines and serotonin. Angiotensin converting enzyme transforms angiotensin I into angiotensin II and breaks down bradykinin into inactive products. Nitric oxide is a potent vasodilator and inhibitor of platelet function that under most circumstances is released together with prostacyclin, which exerts similar effects. Both substances play an important protective role in the coronary circulation in that they cause continuous vasodilation and inhibition of platelet function. In addition, the endothelium is a source of contracting factors such as endothelin-1, thromboxane A2, and endoperoxides. Endothelium-derived growth inhibitors include heparin (sulfates) and transforming growth factor beta 1, while basic fibroblast growth factors and platelet-derived growth factor and possibly endothelin promote proliferation. Because of its strategic anatomic position, the endothelium is a primary target for injuries and cardiovascular risk factors. In particular, aging, low density lipoproteins, hypertension, diabetes, and ischemia alter endothelium function. In arterial coronary bypass grafts, the release of nitric oxide is more pronounced than in vein grafts. Alterations of endothelial function may contribute to vasospasm, thrombus formation, and vascular proliferation and in turn myocardial ischemia, all common events in patients with coronary artery disease.

Expression of cyclin-dependent kinase inhibitors in vascular disease

Arterial lesions in cardiovascular diseases are characterized by proliferation and migration of smooth muscle cells as well as deposition of connective tissue matrix. Factors that stimulate vascular smooth muscle cell (VSMC) proliferation are well described; however, the role of proteins that limit intimal hyperplasia is not well understood. To examine the function of Kip/Cip and INK cyclin-dependent kinase inhibitors (CKIs) in vascular diseases, the expression of p27Kip1 and p16INK was examined in VSMCs in vitro and in porcine arteries and human atherosclerosis in vivo. Western blot and fluorescence activated cell-sorting analysis demonstrated that levels of p27Kip1, but not p16INK, increased during serum deprivation of primary VSMC cultures and caused G1 arrest. p27Kip1 inhibited Cdk2 activity, suggesting that Kip CKIs promote G1 arrest in VSMCs by binding cyclin E/Cdk2. In porcine arteries, p27Kip1, but not p16INK, was constitutively expressed at low levels. Immediately after balloon injury, cell proliferation increased as p27Kip1 levels declined. Three weeks after injury, p27Kip1 was strongly expressed in intimal VSMCs when VSMC proliferation was < 2%, suggesting that p27Kip1 functions as an inhibitor of cell proliferation in injured arteries. In contrast, p16INK expression was detected only transiently early after injury. CKI expression was examined in 35 human coronary arteries, ranging from normal to advanced atherosclerosis. p27Kip1 expression was abundant in nonproliferating VSMCs and macrophages within normal (7 of 8) and atherosclerotic (25 of 27) arteries. p21Cip1 levels were undetectable in normal arteries but were elevated in atherosclerotic (19 of 27) arteries. p16INK could not be detected in normal or atherosclerotic arteries (0 of 35). Thus, the Kip/Cip and INK CKIs have different temporal patterns of expression in VSMCs in vitro and in injured arteries and atherosclerotic lesions in vivo. In contrast to p16INK, p27Kip1 likely contributes to the remodeling process in vascular diseases by the arrest of VSMCs in the G1 phase of the cell cycle.

Nitric oxide modulates expression of cell cycle regulatory proteins: a cytostatic strategy for inhibition of human vascular smooth muscle cell proliferation

BACKGROUND

We examined the effect of NO on the proliferation and cell cycle regulation of human aortic vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

The NO donor diethylenetriamineNONOate (10(-5) to 10(-3) mol/L) inhibited proliferation in response to 10% fetal calf serum (FCS) and 100 ng/mL platelet-derived growth factor-BB in a concentration-dependent manner. This effect was not observed with disintegrated diethylenetriamineNONOate or with the parent compound, diethylenetriamine. Adenoviral transfection of endothelial NO synthase (NOS) inhibited proliferation in response to FCS, which was prevented with N(G)-nitro-L-arginine methyl ester. NOS overexpression did not inhibit proliferation in response to platelet-derived growth factor, although the transfection efficiency and protein expression were similar to those of FCS-stimulated cells. Nitrate release was selectively enhanced from FCS-treated cells, indicating that NOS was activated by FCS only. NO caused G(1) cell cycle arrest. Cytotoxicity was determined with trypan blue exclusion, and apoptosis was assessed with DNA fragmentation. Cyclin-dependent kinase 2 expression level, threonine phosphorylation, and kinase activity were inhibited. Cyclin A expression was blunted, whereas cyclin E remained unchanged. p21 expression was induced, and p27 remained unaltered. The effect on cyclin A and p21 started within 6 hours and preceded the changes in cell cycle distribution. Proliferation in response to 10% FCS was barely inhibited with 8-bromo-cGMP (10(-3) mol/L) but was blunted with both forskolin and 8-bromo-cAMP. Proliferation in response to 2% FCS was inhibited with 8-bromo-cGMP, but it did not mimic the cell cycle effects of NO.

CONCLUSIONS

NO inhibits VSMC proliferation by specifically changing the expression and activity of cell cycle regulatory proteins, which may occur independent of cGMP. Adenoviral overexpression of endothelial NOS represents a cytostatic strategy for gene therapy of vascular disease.

Differential effects of the cyclin-dependent kinase inhibitors p27(Kip1), p21(Cip1), and p16(Ink4) on vascular smooth muscle cell proliferation

BACKGROUND

The cyclin-dependent kinase inhibitors (CKIs) have different patterns of expression in vascular diseases. The Kip/Cip CKIs, p27(Kip1) and p21(Cip1), are upregulated during arterial repair and negatively regulate the growth of vascular smooth muscle cells (VSMCs). In contrast, the Ink CKI, p16(Ink4), is not expressed in vascular lesions. We hypothesized that a variation in the inactivation of cdk2 and cdk4 during the G(1) phase of the cell cycle by p27(Kip1), p21(Cip1), and p16(Ink4) leads to different effects on VSMC growth in vitro and in vivo.

METHODS AND RESULTS

The expression of p27(Kip1) and p21(Cip1) in serum-stimulated VSMCs inactivated cdk2 and cdk4, leading to G(1) growth arrest. p16(Ink4) inhibited cdk4, but not cdk2, kinase activity, producing partial inhibition of VSMC growth in vitro. In an in vivo model of vascular injury, overexpression of p27(Kip1) reduced intimal VSMC proliferation by 52% (P<0.01) and the intima/media area ratio by 51% (P<0.005) after vascular injury and gene transfer to pig arteries, when compared with control arteries. p16(Ink4) was a weak inhibitor of intimal VSMC proliferation in injured arteries (P=NS), and it did not significantly reduce intima/media area ratios (P=NS), which is consistent with its minor effects on VSMC growth in vitro.

CONCLUSIONS

p27(Kip1) and p21(Cip1) are potent inhibitors of VSMC growth compared with p16(Ink4) because of their different molecular mechanisms of cyclin-dependent kinase inhibition in the G(1) phase of the cell cycle. These findings have important implications for our understanding of the pathophysiology of vascular proliferative diseases and for the development of molecular therapies.

Connective tissue growth factor induces apoptosis in human breast cancer cell line MCF-7

Connective tissue growth factor (CTGF) is a member of an emerging CCN gene family that is implicated in various diseases associated with fibro-proliferative disorder including scleroderma and atherosclerosis. The function of CTGF in human cancer is largely unknown. We now show that CTGF induces apoptosis in the human breast cancer cell line MCF-7. CTGF mRNA was completely absent in MCF-7 but strongly induced by treatment with transforming growth factor beta (TGF-beta). TGF-beta by itself induced apoptosis in MCF-7, and this effect was reversed by co-treatment with CTGF antisense oligonucleotide. Overexpression of CTGF gene in transiently transfected MCF-7 cells significantly augmented apoptosis. Moreover, recombinant CTGF protein significantly enhanced apoptosis in MCF-7 cells as evaluated by DNA fragmentation, Tdt-mediated dUTP biotin nick end-labeling staining, flow cytometry analysis, and nuclear staining using Hoechst 33258. Finally, recombinant CTGF showed no effect on Bax protein expression but significantly reduced Bcl2 protein expression. Taken together, these results suggest that CTGF is a major inducer of apoptosis in the human breast cancer cell line MCF-7 and that TGF-beta-induced apoptosis in MCF-7 cells is mediated, in part, by CTGF.

Endothelial regulation of vascular tone and growth

The endothelium regulates vascular tone by releasing factors involved in relaxation and contraction, in coagulation and thrombus formation, and in growth inhibition and stimulation. Endothelium-dependent relaxations are elicited by transmitters, hormones, platelet substances, and the coagulation system, and by physical stimuli such as the shear stress from circulating blood. They are mediated by the endothelium-derived relaxing factor, recently identified as nitric oxide, which causes vasodilation and platelet deactivation. Other proposed endothelium-derived relaxing factors include a hyperpolarizing factor, lipooxygenase products, and the cytochrome P450 pathway. Endothelium-derived contracting factors are produced by the cyclooxygenase pathway and by endothelial cells, which produce the peptide endothelin-1, a potent vasoconstrictor that under normal conditions circulates at low levels. The endothelium produces both growth inhibitors--normally dominant--and growth stimuli. Denuded or dysfunctional endothelium leads to a proliferative response and intimal hyperplasia in the vessel wall; moreover, platelets adhere to the site and release potent growth factors. Endothelial dysfunction has numerous causes: Aging is associated with increased formation of contracting factor and decreased relaxing factor; denudation, such as by coronary angioplasty, impairs the capacities of regenerated endothelial cells; oxidized low-density lipoproteins and hypercholesterolemia interfere with nitric oxide production; hypertension morphologically and functionally alters the endothelium; and atherosclerosis markedly attenuates some endothelium-dependent relaxations. For patients with coronary bypass grafts, differences in endothelium-derived vasoactive factors between the internal mammary artery and the saphenous vein may be important determinants of graft function, with the mammary artery having more pronounced relaxations than the saphenous vein and thus a higher patency rate.

Overexpression of connective tissue growth factor gene induces apoptosis in human aortic smooth muscle cells

BACKGROUND

Connective tissue growth factor (CTGF) is expressed at very high levels particularly in the shoulder of human atherosclerotic lesions but not in normal blood vessels. Thus, CTGF may be important in the regulation of vascular smooth muscle cell function in atherosclerosis, but its precise role remains elusive.

METHODS AND RESULTS

Full-length CTGF cDNA driven by a cytomegalovirus promoter was transiently transfected into cultured human aortic smooth muscle cells (HASCs). Northern and Western analysis demonstrated that CTGF was overexpressed in these cells 48 hours after transfection. The effects of CTGF overexpression on cell proliferation were evaluated by [(3)H]thymidine uptake and cell count in quiescent HASCs or those stimulated with platelet-derived growth factor (PDGF). Although mock transfection showed no effect, CTGF overexpression significantly inhibited cell proliferation in cells stimulated by PDGF. Moreover, CTGF overexpression, but not mock transfection, significantly increased apoptosis as assessed by DNA fragmentation associated with histone, TdT-mediated dUTP biotin nick end-labeling, and appearance of hypodiploid cells by flow cytometry.

CONCLUSIONS

Our results for the first time demonstrate that CTGF can also act as a growth inhibitor in human aortic smooth muscle cells at least in part by inducing apoptosis. This may be important for the formation and composition of lesions and plaque stability in atherosclerosis.

Transfection of human endothelial cells

OBJECTIVE

The introduction of recombinant genes into endothelial cells provides a method to study specific gene products and their effect on cell function. In addition, endothelial cells can be used for implantation into vessels or prosthetic vascular grafts. Because transfection efficiencies in human endothelial cells have been low, it is important to develop improved gene transfer techniques. Therefore, several transfection methods were optimized and transfection efficiencies were determined.

METHODS

Transfection by particle-mediated gene transfer (biolistics) or by cationic liposomes were optimized and compared to calcium phosphate and DEAE-dextran. Transfection efficiency was determined using either a beta-galactosidase or placental alkaline phosphatase reporter gene. The effect of promoter strength was analyzed by transfecting plasmids with either the Rous sarcoma virus (RSV) promoter or cytomegalovirus (CMV) promoter regions.

RESULTS

Optimal conditions for particle-mediated gene transfer utilized gold particles of 1.6 microns diameter, a target distance of 3 cm, helium pressures of 8.96 MPa (1300 psi) and cell confluence of 75%. Transfection with different cationic liposomes demonstrated that one compound, N-(3-aminopropyl)-N,N-dimethyl-2,3-(bis-dodecyloxy)-1-propanimi nium bromide/dioleoyl phosphatidylethanolamine (gamma AP-DLRIE/DOPE), was optimal for gene transfer when 5 micrograms of DNA and 10 to 20 micrograms of lipid was used. With both gold particles and gamma AP-DLRIE/DOPE, the alkaline phosphatase reporter was more efficient than beta-galactosidase using comparable promoters and polyadenylation sites. CMV regulatory elements were more efficient than the RSV promoter in optimizing gene expression. Optimal gene transfer efficiency was 20.28% of cells with gamma AP-DLRIE/DOPE, 3.96% with biolistics, 2.09% with calcium phosphate and 0.88% with DEAE-dextran.

CONCLUSIONS

Gene expression is detectable in a high percentage of human endothelial cells after liposome-mediated transfection when expression is controlled by a strong promoter. Particle-mediated transfection is less efficient under these conditions, but more effective than liposomes when expression is driven by a relatively weak promoter. Calcium phosphate and DEAE-dextran are less useful.

Age, hypertension and hypercholesterolaemia alter endothelium-dependent vascular regulation

As a source of several vasoactive factors, the endothelium takes part in the regulation of vascular tone. The most important endothelium-derived vasoactive substances are nitric oxide, prostacyclin, endothelin-1 and contracting factors requiring the activity of cyclooxygenase. The endothelium is an obvious target organ of cardiovascular risk factors. Accordingly, functional alterations do occur with aging, hypertension and hypercholesterolaemia. All three conditions are associated with a decreased basal and simulated release of endothelium-derived nitric oxide. On the other hand, the release of endothelin-1 appears to increase with age, while the sensitivity to the peptide markedly decreases under the same conditions. In the spontaneously hypertensive rat, acetylcholine and stretch evoke the release of a cyclooxygenase-dependent endothelium-derived contracting factor, most likely prostaglandin H2. The circulating levels of endothelin-1 on the other hand are not increased in experimental and human hypertension. In the porcine coronary circulation, oxidized low-density lipoproteins selectively reduced endothelium-dependent relaxations to aggregating platelets, serotonin and thrombin which are mediated by nitric oxide. The alterations of endothelial function occurring with aging, hypertension and hypercholesterolaemia may have important clinical implications for the pathogenesis of cardiovascular disease.

Lipids and endothelial function: effects of lipid-lowering and other therapeutic interventions

Coronary arteries are regulated by neuronal mechanisms, hormones and paracrine mediators. The importance of endothelium-dependent mechanisms has recently been recognized. The endothelium responds to mechanical and chemical signals from the blood by releasing mediators that modulate vascular tone and structure, platelet function, coagulation and monocyte adhesion. Important relaxing factors are nitric oxide, prostacyclin and a putative hyperpolarizing factor. Nitric oxide also inhibits smooth muscle proliferation and, together with prostacyclin, platelet function. Bradykinin-induced nitric oxide production is reduced by angiotensin-converting enzyme. Endothelin-1, thromboxane A2 and prostaglandin H2 are contracting factors. Thromboxane A2 and prostaglandin H2 activate platelets, while endothelin has no direct platelet effects, but causes smooth muscle proliferation. In hypercholestermia, endothelium-dependent relaxation is impaired and contraction as well as adhesion of monocytes and platelets enhanced. Pharmacological correction of hyperlipidemia by statins also improves or normalizes endothelial dysfunction in patients. Angiotensin-converting enzyme inhibitors have similar effects.

Endothelium-derived nitric oxide, endothelin, and platelet vessel wall interaction: alterations in hypercholesterolemia and atherosclerosis

The endothelium modulates vascular tone by releasing NO, which is a potent vasodilator and inhibitor of platelet aggregation. Thus, the endogenous nitrate has an important protective role in preventing vasospasm and thrombus formation. In addition, the endothelium is a source of contracting factors, such as endothelin-1. Due to its strategical anatomic position, the endothelium is a primary target for injurious stimuli and cardiovascular risk factors. Oxidized LDL reduce the endothelial production of NO and enhance that of endothelin-1. The same pattern of endothelial dysfunction occurs in hypercholesterolemia and in part in atherosclerosis. These alterations of endothelial function may contribute to vasospasm and thrombus formation, which are common events in patients with atherosclerosis.

Different activation of L-arginine pathway by bradykinin, serotonin, and clonidine in coronary arteries

Endothelial cells release nitric oxide from L-arginine, and this pathway can be inhibited by the analogue of L-arginine, NG-monomethyl-L-arginine (L-NMMA). The effect of L-NMMA on endothelium-dependent relaxation of epicardial porcine coronary arteries was studied in isolated blood vessels suspended in organ chambers for isometric tension recording. Endothelium-dependent relaxations to bradykinin, serotonin, and the alpha 2-adrenergic agonist clonidine were evaluated in the presence and absence of L-NMMA (10(-5)-10(-3) M). L-NMMA, as well as the inhibitor of guanylate cyclase methylene blue (10(-5) M) and hemoglobin (10(-5) M), inhibited endothelium-dependent relaxation to serotonin and clonidine. The effect of L-NMMA could be reversed by L-arginine but not by D-arginine. In contrast, L-NMMA, methylene blue, and hemoglobin caused a weak inhibition of the endothelium-dependent relaxation evoked by bradykinin; indomethacin and tranylcypromine had no effect. The inhibitor of Gi proteins pertussis toxin (100 ng/ml) abolished the relaxations evoked by clonidine and markedly reduced those evoked by serotonin but did not affect those caused by bradykinin. In the presence of pertussis toxin, L-NMMA induced a further reduction of the relaxations to serotonin, suggesting that inhibition of Gi proteins does not completely prevent the activation of the L-arginine pathway. Thus endothelium-dependent relaxations to serotonin and to the alpha 2-adrenergic agonist clonidine are mediated through the release of nitric oxide formed from L-arginine in endothelial cells, whereas bradykinin evokes endothelium-dependent relaxations via a different pathway.

In vivo gene delivery to the pulmonary circulation in rats: transgene distribution and vascular inflammatory response

Although gene delivery to the pulmonary circulation has both experimental and therapeutic potential, the delivery methods, distribution of transgene, and subsequent inflammatory response have been poorly characterized to date. To address these issues, we utilized a 0.76-mm OD (outside diameter) end hole catheter inserted into the internal jugular vein of adult Sprague-Dawley rats, directing the tip into a pulmonary capillary wedge position. We then compared infusion of polycationic lipid:DNA complexes to replication-defective adenovirus with respect to magnitude and distribution of transgene expression using either chloramphenicol acetyltransferase (CAT) or human placental alkaline phosphatase (hpAP) reporter genes. Both lipid:DNA and adenovirus resulted in detectable transgene expression, though maximum lung CAT activity using lipid (gamma AP-DLRIE/DOPE) was approximately 2% of maximum activity using adenovirus (Ad-CAT). Further characterization of expression after transfection with 10(8) pfu (plaque forming units) of Ad-CAT demonstrated persistence of transgene for at least 14 days (lung CAT activity 27% of maximum). Alkaline phosphatase staining demonstrated that both large and small pulmonary arteries as well as the alveolar wall expressed transgene. Although little inflammatory response was detected in conduit arteries, a predominantly mononuclear cell infiltrate surrounded small pulmonary arteries as well as the alveolar spaces in transfected areas of lung. We conclude that percutaneous catheter-mediated gene delivery to the pulmonary circulation in rats using non-viral and viral vectors is feasible. Although an inflammatory response to first generation replication-defective adenovirus was detected, it appeared to be largely restricted to the distal pulmonary circulation and airspace. This technique should prove useful for investigations requiring overexpression of novel genes in the pulmonary artery wall, and could ultimately be used to develop gene-based therapies for pulmonary vascular diseases.

Prothrombotic gene expression profile in vascular smooth muscle cells of human saphenous vein, but not internal mammary artery

BACKGROUND

The resistance of internal mammary artery (IMA) toward thrombotic occlusion and accelerated atherosclerosis is not well understood. This study analyzed gene expression profiles of vascular smooth muscle cells (VSMCs) from IMA versus saphenous vein (SV).

METHODS AND RESULTS

54'675 probe sets were examined by Affymetrix microarrays. Thirty-one genes belonged to the coagulation system; 2 were differentially expressed, namely tissue factor (TF) and tissue-type plasminogen activator (tPA). TF was 3.1-fold lower in IMA than SV (P=0.006), whereas tPA was 9.0-fold higher (P<0.001). TF mRNA expression was lower in IMA than SV (P<0.05); tPA was higher (P<0.001). TF protein expression was 4.2+/-0.5-fold lower in IMA than SV (P<0.001); tPA was 2.6+/-0.4-fold higher (P<0.01). In IMA VSMC supernatant, TF protein and activity was lower (P<0.05), TFPI and tPA protein higher (P<0.05 and P<0.005), and clotting time of human plasma prolonged (P<0.05) as compared to SV. Migration to TF/FVIIa (10(-9) mol/L) was 3-fold lower in IMA than SV (P=0.01); PAR-2 protein expression was similar (P=NS), PAR-2 blockade without effect (P=NS).

CONCLUSIONS

Among the genes of the coagulation system, TF and tPA are differentially expressed in VSMCs from IMA versus SV. This is consistent with protection of IMA from thrombus formation and vascular remodeling.

[Echinococcus multilocularis in Grisons: distribution in foxes and presence of potential intermediate hosts]

The southern border of the European endemic area of Echinococcus multilocularis runs along the alpine crest. This endemic transition area was analysed in the canton Grisons on a small spatial scale. A total of 543 foxes originating from 10 areas north and 4 areas south of the main alpine divide were investigated. Parasites were isolated using the sedimentation and counting technique on intestinal contents. The mean prevalence of E. multilocularis was 6.4% with significant differences between different areas. In the southern valleys, only foxes from the Val Müstair were infected (14.3%). On the northern side of the main alpine divide, prevalences varied between 0 and 40%. The predation habits of foxes on potential intermediate hosts was investigated by means of stomach content analyses (n=530). Rodents of the genera Microtus/Pitymys were found in 19.6% of fox stomachs, Clethrionomys glareolus in 8.0% and Arvicola terrestris in 0.4%. A small scale analysis based on a 10 x 10 km grid suggested that the predation rate on the genera Microtus/Pitymys significantly correlated with the prevalence of E. multilocularis in foxes (Spearman's r = 0.51). Hence, E. multilocularis appears to occur in the alpine study area on a very small spatial scale. These local sources of infection may persist for decades. This may partly explains why, during the last 34 years, some human cases of alveolar echinococcosis occurred in areas of the Canton Grisons where the parasite is presently endemic in foxes. No such human cases have been recorded in other areas free of E. multilocularis.

Amiodarone inhibits arterial thrombus formation and tissue factor translation

BACKGROUND

In patients with coronary artery disease and reduced ejection fraction, amiodarone reduces mortality by decreasing sudden death. Because the latter may be triggered by coronary artery thrombosis as much as ventricular arrhythmias, amiodarone might interfere with tissue factor (TF) expression and thrombus formation.

METHODS AND RESULTS

Clinically relevant plasma concentrations of amiodarone reduced TF activity and impaired carotid artery thrombus formation in a mouse photochemical injury model in vivo. PTT, aPTT, and tail bleeding time were not affected; platelet number was slightly decreased. In human endothelial and vascular smooth muscle cells, amiodarone inhibited tumor necrosis factor (TNF)-alpha and thrombin-induced TF expression as well as surface activity. Amiodarone lacking iodine and the main metabolite of amiodarone, N-monodesethylamiodarone, inhibited TF expression. Amiodarone did not affect mitogen-activated protein kinase activation, TF mRNA expression, and TF protein degradation. Metabolic labeling confirmed that amiodarone inhibited TF protein translation.

CONCLUSIONS

Amiodarone impairs thrombus formation in vivo; in line with this, it inhibits TF protein expression and surface activity in human vascular cells. These pleiotropic actions occur within the range of amiodarone concentrations measured in patients, and thus may account at least in part for its beneficial effects in patients with coronary artery disease.

Histamine differentially interacts with tumor necrosis factor-alpha and thrombin in endothelial tissue factor induction: the role of c-Jun NH2-terminal kinase

BACKGROUND

Histamine plays an important role in vascular disease. Tissue factor (TF) expression is induced in vascular inflammation and acute coronary syndromes.

OBJECTIVES

This study examined the effect of histamine on tumor necrosis factor-alpha- (TNF-alpha-) vs. thrombin-induced endothelial TF expression.

METHODS AND RESULTS

Histamine (10(-8)-10(-5) mol L-1), TNF-alpha (5 ng mL-1), and thrombin (1 U mL-1) induced TF expression in human endothelial cells. Although TF expression by TNF-alpha and thrombin was identical, histamine augmented TNF-alpha-induced expression 7.0-fold, but thrombin-induced expression only 2.6-fold. Similar responses occurred with TF activity. The H1-receptor antagonist mepyramine abrogated these effects. Differential augmentation by histamine was also observed at the mRNA level. Histamine-induced p38 activation preceded a weak second activation to both TNF-alpha and thrombin. Histamine-induced c-Jun NH2-terminal kinase (JNK) activation was followed by a strong second activation to TNF-alpha, and less to thrombin. Selective inhibition of this second JNK activation by SP600125 reduced TF induction to histamine plus TNF-alpha by 67%, but to histamine plus thrombin by only 32%. Histamine augmented TNF-alpha- and thrombin-induced vascular cell adhesion molecule 1 (VCAM-1) expression to a similar extent. Consistent with this observation, VCAM-1 induction to TNF-alpha and thrombin was mediated by p38, but not by JNK.

CONCLUSIONS

Histamine differentially augments TNF-alpha- vs. thrombin-induced TF expression and activity, which is mediated by the H1-receptor, occurs at the mRNA level, and is related to differential JNK activation.

Mitral annular calcification in the elderly - Quantitative assessment

PURPOSE

To determine the reliability of subjective and objective quantification of mitral annular calcification (MAC) in elderly patients with severe aortic stenosis, to define quantitative sex- and age-related reference values of MAC, and to correlate quantitative MAC with mitral valve disease.

METHODS

In this retrospective, IRB-approved study, we included 559 patients (268 females, median age 81 years, inter-quartile range 77-85 years) with severe aortic stenosis undergoing CT. Four independent readers performed subjective MAC categorization as follows: no, mild, moderate, and severe MAC. Two independent readers performed quantitative evaluation of MAC using the Agatston score method (Agatston_MAC). Mitral valve disease was determined by echocardiography.

RESULTS

Subjective MAC categorization showed high inter-reader agreement for no (k ​= ​0.88) and severe MAC (k ​= ​0.75), whereas agreement for moderate (k ​= ​0.59) and mild (k ​= ​0.45) MAC was moderate. Intra-reader agreement for subjective MAC categorization was substantial (k ​= ​0.69 and 0.62). Inter- and intra-reader agreement for Agatston_MAC were excellent (ICC ​= ​0.998 and 0.999, respectively), with minor inconsistencies in MAC involving the left ventricular outflow tract/aortic valve. There were significantly more women than men with MAC (n ​= ​227, 85% versus n ​= ​209, 72%; p ​< ​0.001), with a significantly higher Agatston_MAC (median 597, range 81-2055 versus median 244; range 0-1565; p ​< ​0.001), particularly in patients ≥85 years of age. Agatston_MAC showed an area-under-the-curve of 0.84 to diagnose mitral stenosis, whereas there was no association of Agatston_MAC with mitral regurgitation (p ​> ​0.05).

CONCLUSIONS

Our study in elderly patients with severe aortic stenosis shows that quantitative MAC scoring is more reliable than subjective MAC assessment. Women show higher Agatston_MAC scores than men, particularly in the elderly population. Agatston_MAC shows high accuracy to diagnose mitral stenosis.

A Prospective Pilot Study to Identify a Myocarditis Cohort who may Safely Resume Sports Activities 3 Months after Diagnosis

International cardiovascular society recommendations to return to sports activities following acute myocarditis are based on expert consensus in the absence of prospective studies. We prospectively enrolled 30 patients with newly diagnosed myocarditis based on clinical parameters, laboratory measurements and cardiac magnetic resonance imaging with mildly reduced or preserved left ventricular ejection fraction (LVEF) with a follow-up of 12 months. Cessation of physical activity was recommended for 3 months. The average age was 35 (19-80) years with 73% male patients. One case of non-sustained ventricular tachycardia was recorded during 48-h-Holter electrocardiogram. Except for this case, all patients were allowed to resume physical exercise after 3 months. At 6- (n = 26) and 12-month (n = 19) follow-up neither cardiac events nor worsening LVEF were recorded. The risk of cardiac events at 1 year after diagnosis of myocarditis appears to be low after resumption of exercise after 3 months among patients who recover from acute myocarditis.

Endothelium-dependent control of vascular tone: effects of age, hypertension and lipids

As a source of several vasoactive factors, the endothelium takes part in the regulation of vascular tone. The most important endothelium-derived vasoactive substances are nitric oxide, prostacyclin, endothelin-1 and contracting factors requiring the activity of cyclooxygenase. The endothelium is an obvious target organ of cardiovascular risk factors. Accordingly, functional alterations do occur with aging, hypertension, and lipids. All three conditions are associated with a decreased basal and stimulated release of endothelium-derived nitric oxide. On the other hand, the release of endothelin-1 appears to increase with age, while the sensitivity to the peptide markedly decreases under the same conditions. In the spontaneously hypertensive rat, acetylcholine and stretch evoke the release of cyclooxygenase-dependent endothelium-derived contracting factor, most likely prostaglandin H2. The sensitivity and circulating levels of endothelin-1, on the other hand, are reduced in this experimental model of hypertension. In the porcine coronary circulation, oxidized low-density lipoproteins selectively reduce endothelium-dependent relaxations to aggregating platelets, serotonin, and thrombin which are mediated by nitric oxide. The alterations of endothelial function occurring with aging, hypertension, and hyperlipidemia may have important clinical implications for the pathogenesis of cardiovascular disease.

Mitral annular disjunction in patients with severe aortic stenosis: Extent and reproducibility of measurements with computed tomography

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Mitral annulus disjunction (MAD) is frequent in patients with severe aortic stenosis.

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Computed tomography enables a highly reproducible assessment of MAD.

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MAD patients significantly more often have mitral valve prolapse.

Objectives

To determine with CT the prevalence and extent of mitral annular disjunction (MAD) in patients undergoing transcatheter aortic valve replacement (TAVR) and its association with mitral valve disease and arrhythmia.

Methods

We retrospectively evaluated 408 patients (median age, 82 years; 186 females) with severe aortic stenosis undergoing ECG-gated cardiac CT with end-systolic data acquisition. Baseline and follow-up data were collected in the context of a national registry. Two blinded, independent observers evaluated the presence of MAD on multi-planar reformations. Maximum MAD distance (left atrial wall-mitral leaflet junction to left ventricular myocardium) and circumferential extent of MAD were assessed on CT using dedicated post-processing software. Associated mitral valve disease was determined with echocardiography.

Results

7.8 % (32/408) of patients with severe aortic stenosis had MAD. The maximum MAD was 3.5 mm (interquartile range: 3.0–4.0 mm). The circumferential extent of MAD comprised 34 ± 15 % of the posterior and 26 ± 12 % of the entire mitral annulus. Intra- and interobserver agreement for the detection of MAD on CT were excellent (kappa: 0.90 ± 0.02 and 0.92 ± 0.02). Mitral regurgitation (p = 1.00) and severe mitral annular calcification (p = 0.29) were similarly prevalent in MAD and non-MAD patients. Significantly more patients with MAD (6/32; 19 %) had mitral valve prolapse compared to those without (6/376; 2 %; p < 0.001). MAD was not associated with arrhythmia before and after TAVR (p > 0.05).

Conclusions

Using CT, MAD was found in 7.8 % of patients with severe aortic stenosis, with a higher prevalence in patients with mitral valve prolapse. We found no association of MAD with arrhythmia before or after TAVR.