Arteriosclerosis Thrombosis and Vascular Biology

Published by American Heart Association
Online ISSN: 1524-4636
Print ISSN: 1079-5642
Publications
In a double-blind, randomized, crossover study, we investigated in 15 healthy male volunteers the effects of recombinant (r-) hirudin (HBW 023, 0.35 mg/kg body wt SC), unfractionated heparin (UFH, HeparinNovo; 150 IU/kg body wt SC), and a low-molecular-weight heparin preparation (LMWH, Fragmin; 75 IU/kg body wt SC) on coagulation and platelet activation in vivo by measuring specific coagulation-activation peptides (prothrombin fragment 1 + 2 [F1 + 2], thrombin-antithrombin-III complex [TAT], and beta-thromboglobulin [beta-TG]) in bleeding-time blood (activated state) and venous blood (basal state). In bleeding-time blood, r-hirudin and the heparin preparations significantly inhibited formation of both TAT and F1 + 2. However, the inhibitory effect of r-hirudin on F1 + 2 generation was short-lived and weaker compared with that of UFH and LMWH, and the TAT-to-F1 + 2 ratio was significantly lower after r-hirudin than after UFH or LMWH. Thus, in vivo, when the coagulation system is in an activated state, r-hirudin exerts its anticoagulant effects predominantly by inhibiting thrombin (factor IIa), whereas UFH and LMWH are directed against both factors Xa and IIa. A different mode of action for UFH and LMWH was not detectable. In venous blood, r-hirudin caused a moderate reduction in TAT formation and an increase (at 1 hour) rather than a decrease in F1 + 2 generation. Formation of TAT and F1 + 2 was suppressed at various time points following both UFH and LMWH. There was no difference in the TAT-to-F1 + 2 ratio after r-hirudin and heparin.(ABSTRACT TRUNCATED AT 250 WORDS)
 
We examined the effect of acyl-coenzyme A:cholesterol acyltransferase (ACAT) inhibitors on intracellular cholesterol stores in primary human monocyte-derived macrophages (HMMs) during foam cell formation. HMMs were exposed to acetylated low density lipoprotein (acLDL, 500 microg protein per mL) with or without 58-035 (1 to 10 microg/mL) or CI-976 (2 microg/mL) for 2 to 48 hours. Total cholesterol (TC) and esterified cholesterol (EC) mass was significantly lower while unesterified cholesterol (UC) increased slightly in cells incubated with acLDL plus ACAT inhibitors. Sterol mass was also measured in cells coincubated with acLDL (500 microg protein per mL) with or without 58-035 (2 microg/mL), high density lipoprotein (HDL, 400 microg protein per mL), or HDL+58-035 for 48 hours. TC and EC were 23% and 55% lower, respectively (P<0.0004), while UC was 11% higher (P<0.04) in cells incubated with acLDL plus 58-035. In contrast, coincubation with HDL alone did not significantly affect TC, EC, or UC mass compared with acLDL alone. The effect of 58-035 could not be explained by cytotoxicity, because adenine release, secreted lactate dehydrogenase, glucose utilization, and cell protein were similar in cells exposed to acLDL regardless of the presence of 58-035. We investigated several potential mechanisms for the decreased TC mass, including increased UC efflux and decreased acLDL binding and uptake. Efflux was measured in cells exposed to [1,2-(3)H]cholesteryl oleate-labeled acLDL, unlabeled control acLDL, and native untreated acLDL (500 microg protein per mL) with or without 58-035 (5 microg/mL) for 24 or 48 hours. UC efflux increased in a time-dependent manner from cells exposed to acLDL plus 58-035 compared with cells exposed to acLDL alone (P<0. 04). High-affinity binding was measured in cells exposed to (125)I-acLDL (5 microg protein per mL) with or without excess unlabeled acLDL (100 or 500 microg protein per mL) for 4 hours at 4 degrees C. Specific acLDL binding, uptake, and total degradation were significantly lower when 58-035 was present during cholesterol enrichment compared with cells exposed to acLDL alone (P<0.001). Unlike the effects of ACAT inhibitors on foam cell formation in rodent macrophages, these compounds lowered TC accumulation in HMMs during foam cell formation by limiting the uptake of acLDL and enhancing UC efflux. They may offer promise as drug therapies for atherosclerosis.
 
We demonstrate that physiological concentrations of HDL3 inhibit the thrombin-induced platelet fibrinogen binding and aggregation in a time- and concentration-dependent fashion. The underlying mechanism includes HDL3-mediated inhibition of phosphatidylinositol 4,5-bis-phosphate turnover, 1,2-diacylglycerol and inositol 1,4,5-tris-phosphate formation, and intracellular calcium mobilization. The inhibitory effects of HDL3 on inositol 1,4,5-tris-phosphate formation and intracellular calcium mobilization were abolished after covalent modification of HDL3 with dimethylsuberimidate. Furthermore, they could be blocked by calphostin C and bis-indolylmaleimide, 2 highly selective and structurally unrelated protein kinase C inhibitors. However, the inhibitory effects of HDL3 were not blocked by H89, a protein kinase A inhibitor. In addition, HDL3 failed to induce cAMP formation but stimulated the phosphorylation of the protein kinase C 40- to 47-kD major protein substrate. We observed a close temporal relationship between the HDL3-mediated inhibition of thrombin-induced inositol 1,4,5-tris-phosphate formation, intracellular calcium mobilization, and fibrinogen binding and the phosphorylation of the protein kinase C 40- to 47-kD major protein substrate. Taken together, these findings indicate that the HDL3-mediated inhibition of thrombin-induced fibrinogen binding and aggregation occurs via inhibition of phosphatidylinositol 4,5-bis-phosphate turnover and formation of 1,2-diacylglycerol and inositol 1,4,5-tris-phosphate. Protein kinase C may be involved in this process.
 
These studies examine the contributions of alpha(1,3)fucosyltransferases (FucT) IV and VII to the generation of selectin counter-receptors necessary for selectin-dependent atherogenesis. They also determine the functional contribution of FucT-IV and FucT-VII to shear-dependent tethering of monocytes to P-selectin, a process believed to be required for atherogenesis. Atherosclerotic lesion size and histology were determined in apolipoprotein E-/- mice sufficient or deficient in FucT-IV or FucT-VII. Lesion size was subtly reduced in FucT-IV-deficient mice and significantly reduced in FucT-VII-deficient mice. FucT deficiency did not alter lesion histology, plasma total cholesterol, or the lipoprotein distribution profile. Atheroprotection in FucT-IV or FucT-VII deficiency aligned with subtle and profound reductions, respectively, of P-selectin counter-receptor activity on peripheral blood monocytes as determined by tethering to P-selectin-IgG in vitro under shear flow. FucT-VII-mediated alpha(1,3)fucosylation of selectin ligands is a necessary concomitant to atherogenesis in apoE-/- mice and is required for P-selectin-dependent peripheral blood monocyte adhesion under shear stress. FucT-IV deficiency yields subtle deficits in monocyte P-selectin counter-receptor activity and is associated with a subtle decrement in atherosclerosis. These studies identify an important role for FucT-VII in atherogenesis, and a subsidiary role for FucT-IV, and implicate leukocyte selectin counter-receptors in the pathogenesis of atherosclerosis.
 
Apolipoprotein (apo) E-deficient mice develop atherosclerotic lesions that contain epitopes formed during the oxidative modification of lipoproteins, and they demonstrate high titers of circulating autoantibodies against such epitopes, suggesting that this murine strain may provide a model to investigate the atherogenic mechanisms of oxidized lipoproteins (Palinski et al, Arterioscler Thromb. 1994; 14:605-616). To test the hypothesis that lipoprotein oxidation contributes to lesion formation in apoE-deficient mice, we studied the effect of the antioxidant N,N'-diphenyl 1,4-phenylenediamine (DPPD) in mice fed a high-fat diet containing 0.15% cholesterol. Animals were divided into two subgroups matched for sex and plasma cholesterol levels, and DPPD (0.5% wt/wt) was added to the diet of one subgroup. Throughout the 6 months of intervention, DPPD treatment had no significant effect on plasma cholesterol. Plasma levels of DPPD at the end of the experiment were 33.1 mumol/L. As judged by resistance to loss of polyunsaturated fatty acids, lipoproteins (d < 1.019 g/mL) from DPPD-treated animals showed greater resistance to copper-induced oxidation than lipoproteins from control animals. In addition, there was a greater than twofold prolongation of the lag time in the formation of conjugated dienes in the LDL and IDL fractions of DPPD-treated mice. Atherosclerosis was significantly reduced, by 36% in the DPPD-treated mice (14.0 +/- 4.53% of aortic surface area versus 21.9 +/- 11.6%; n = 32; P < .02). These results are consistent with the hypothesis that lipoprotein oxidation contributes to atherogenesis in apoE-deficient mice. However, further studies with other antioxidants are needed to validate this hypothesis.
 
The aim of this study was to correlate the expression of InsP3R subtypes in native vascular and visceral myocytes with specific Ca2+-signaling patterns. By Western blot and immunostaining, we showed that rat portal vein expressed InsP3R1 and InsP3R2 but not InsP3R3, whereas rat ureter expressed InsP3R1 and InsP3R3 but not InsP3R2. Acetylcholine induced single Ca2+ responses in all ureteric myocytes but only in 50% of vascular myocytes. In the remaining vascular myocytes, the first transient peak was followed by Ca2+ oscillations. By correlating Ca2+ signals and immunostaining, we revealed that oscillating vascular cells expressed both InsP3R1 and InsP3R2 whereas nonoscillating vascular cells expressed only InsP3R1. Acetylcholine-induced oscillations were not affected by inhibitors of ryanodine receptors, Ca2+-ATPases, Ca2+ influx, and mitochondrial Ca2+ uniporter but were inhibited by intracellular infusion of heparin. Using specific antibodies against InsP3R subtypes, we showed that acetylcholine-induced Ca2+ oscillations were specifically blocked by the anti-InsP3R antibody. These data were supported by antisense oligonucleotides targeting InsP3R2, which selectively inhibited Ca2+ oscillations. Our results suggest that in native smooth muscle cells, a differential expression of InsP3R subtypes encodes specific InsP3-mediated Ca2+ responses and that the presence of the InsP3R2 subtype is required for acetylcholine-induced Ca2+ oscillations in vascular myocytes.
 
The IP3 receptor-1 (IP3R1) mediates Ca2+ signals critical to vascular smooth muscle cell (VSMC) proliferation. The cell cycle-associated transcription factor c-Myb increases Ca2+ at the G1/S transition. Here we show the mechanism through which c-Myb regulates expression of IP3R1. Ribonuclease protection confirmed transcriptional start (TS), and qRT-PCR revealed a 6-fold increase in IP3R1 mRNA as immortalized VSMC progress from G0 to G1/S. A c-Myb neutralizing antibody decreased IP3R1 mRNA expression 3-fold, and abolished the 3.4-fold increase in IP3R1 protein observed at G1/S. Primary aortic VSMCs in culture and proliferating carotid VSMCs in vivo showed similar regulation of IP3R1 mRNA and protein. Sequence analysis of a 3.1-Kb mouse IP3R1 promoter revealed 17 putative c-Myb binding sites. Reporter assays demonstrated a 2-fold increase in promoter activity in G1/S- versus G0-synchronized VSMCs, which was abolished by functional c-Myb knockdown or deletion of promoter sequences upstream and downstream of TS. Point mutations in Myb sites-13 or -15 significantly blunted G1/S-specific promoter induction in both immortalized and primary VSMCs. Gel shift and ChIP confirmed binding of c-Myb to sites-13 and -15 in G1/S stage VSMCs. c-Myb regulates cell cycle-associated IP3R1 transcription in VSMCs via specific highly conserved Myb-binding sites in the IP3R1 promoter.
 
8-Hydroxy-2,2,14,14-tetramethylpentadecanedioic acid (ETC-1002) is a small molecule with a unique mechanism of action shown in nonclinical studies to modulate pathways of cholesterol, fatty acid, and carbohydrate metabolism. In previous phase 2 clinical trials, once daily oral treatment with ETC-1002 significantly reduced low-density lipoprotein-cholesterol in patients with hypercholesterolemia. In this trial, the lipid-lowering efficacy of ETC-1002 was evaluated in patients with type 2 diabetes mellitus and hypercholesterolemia. Additional cardiometabolic biomarkers, including glycemic measures, were also assessed. A single-center, double-blind, placebo-controlled trial evaluated 60 patients with type 2 diabetes mellitus and elevated low-density lipoprotein-cholesterol. Patients discontinued all diabetes mellitus and lipid-regulating drugs and were randomized to receive ETC-1002 80 mg QD for 2 weeks followed by 120 mg QD for 2 weeks or placebo for 4 weeks. ETC-1002 lowered low-density lipoprotein-cholesterol levels by 43±2.6% (least squares mean±SE), compared with a reduction of 4±2.5% by placebo at day 29 (P<0.0001; primary end point). Non-high-density lipoprotein-cholesterol and total cholesterol were also significantly lowered by ETC-1002 compared with placebo (P<0.0001). High-sensitivity C-reactive protein was reduced by 41% (median) compared with a placebo reduction of 11% (P=0.0011). No clinically meaningful safety findings were observed. ETC-1002 lowered low-density lipoprotein-cholesterol and other lipids and demonstrated improvement in high-sensitivity C-reactive protein in patients with type 2 diabetes mellitus and hypercholesterolemia without worsening glycemic control. ETC-1002 was well tolerated in this population. http://www.clinicaltrials.gov. Unique identifier: NCT# 01607294.
 
Gestational diabetes mellitus (GDM) produces fetal hyperglycemia with increased lifelong risks for the exposed offspring of cardiovascular and other diseases. Epigenetic mechanisms induce long-term gene expression changes in response to in utero environmental perturbations. Moreover, microRNAs (miRs) control the function of endothelial cells (ECs) under physiological and pathological conditions and can target the epigenetic machinery. We investigated the functional and expressional effect of GDM on human fetal ECs of the umbilical cord vein (HUVECs). We focused on miR-101 and 1 of its targets, enhancer of zester homolog-2 (EZH2), which trimethylates the lysine 27 of histone 3, thus repressing gene transcription. EZH2 exists as isoforms α and β APPROACH AND RESULTS: HUVECs were prepared from GDM or healthy pregnancies and tested in apoptosis, migration, and Matrigel assays. GDM-HUVECs demonstrated decreased functional capacities, increased miR-101 expression, and reduced EZH2- β and trimethylation of histone H3 on lysine 27 levels. MiR-101 inhibition increased EZH2 expression and improved GDM-HUVEC function. Healthy HUVECs were exposed to high or normal d-glucose concentration for 48 hours and then tested for miR-101 and EZH2 expression. Similar to GDM, high glucose increased miR-101 expression. Chromatin immunoprecipitation using an antibody for EZH2 followed by polymerase chain reaction analyses for miR-101 gene promoter regions showed that both GDM and high glucose concentration reduced EZH2 binding to the miR-101 locus in HUVECs. Moreover, EZH2-β overexpression inhibited miR-101 promoter activity in HUVECs. GDM impairs HUVEC function via miR-101 upregulation. EZH2 is both a transcriptional inhibitor and a target gene of miR-101 in HUVECs, and it contributes to some of the miR-101-induced defects of GDM-HUVECs. © 2015 American Heart Association, Inc.
 
The concept that hepatic cholesteryl ester (CE) mass and the rate of cholesterol esterification regulate hepatocyte assembly and secretion of apoB-containing lipoproteins remains controversial. The present study was carried out in HepG2 cells to correlate the rate of cholesterol esterification and CE mass with apoB secretion by CI-1011, an acyl CoA:cholesterol acyltransferase (ACAT) inhibitor that is known to decrease apoB secretion, in vivo, in miniature pigs. HepG2 cells were incubated with CI-1011 (10 nmol/L, 1 micromol/L, and 10 micromol/L) for 24 hours. ApoB secretion into media was decreased by 25%, 27%, and 43%, respectively (P<0.0012). CI-1011 (10 micromol/L) inhibited HepG2 cell ACAT activity by 79% (P<0.002) and cellular CE mass by 32% (P<0.05). In contrast, another ACAT inhibitor, DuP 128 (10 micromol/L), decreased cellular ACAT activity and CE mass by 85% (P<0.002) and 42% (P=0.01), respectively, but had no effect on apoB secretion into media. To characterize the reduction in apoB secretion by CI-1011, pulse-chase experiments were performed and analyzed by multicompartmental modelling using SAAM II. CI-1011 did not affect the synthesis of apoB or albumin. However, apoB secretion into the media was decreased by 42% (P=0.019). Intracellular apoB degradation increased proportionately (P=0.019). The secretion of albumin and cellular reuptake of labeled lipoproteins were unchanged. CI-1011 and DuP 128 did not affect apoB mRNA concentrations. These results show that CI-1011 decreases apoB secretion by a mechanism that involves an enhanced intracellular degradation of apoB. This study demonstrates that ACAT inhibitors can exert differential effects on apoB secretion from HepG2 cells that do not reflect their efficacy in inhibiting cholesterol esterification.
 
Effect of HCT-1026 and flurbiprofen on medial (open bars) and neointimal (solid bars) areas of injured rat carotid arteries. Results are expressed as meanSEM. ***P0.001 vs control group. 
Immunohistochemical staining for PCNA (red nuclear staining), indicating proliferating cells. Neointima from untreated vessel segment (A), neointima from HCT-1026 (30 mg/kg)-treated segment (B), and neointima from flurbiprofen (21 mg/kg)-treated segment (C) 14 days after balloon injury are shown. 
Representative Western blot of iNOS (A) and densitometric analysis (B) showing the effect of HCT-1026 (30 mg/kg) and flurbiprofen (Flurbi, 21 mg/kg) on iNOS protein expression in injured rat carotid arteries. Results are expressed as meanSEM of 3 separate experiments. 
One of the major problems related to the percutaneous transluminal coronary angioplasty technique is the renarrowing of the vessel, a phenomenon known as restenosis. NO and nonsteroidal anti-inflammatory drugs have been shown to play a role in this pathology. The main problem with the use of conventional NO donors is that they affect blood pressure and flow, and for these reasons, they cannot be used safely in clinical practice. The aim of this study was to evaluate, with the use of a rat model of balloon angioplasty, whether a structural derivative of flurbiprofen, containing an added NO-releasing moiety (HCT-1026), is able to reduce or prevent neointimal formation. Rats were treated for 14 days with equimolar doses of flurbiprofen (2, 7, and 21 mg/kg) or HCT-1026 (3, 10, and 30 mg/kg). After this 14-day treatment, HCT-1026 but not flurbiprofen significantly modified the neointima/media ratio. The reduction in the neointimal proliferation obtained with HCT-1026 was well correlated with an increase in nitrite/nitrate plasma levels and a reduced cell proliferation. Neither HCT-1026 nor flurbiprofen affected inducible NO synthase induction in injured vessels. In conclusion, HCT-1026 caused a significant reduction in restenosis that appears to be directly related to NO release. HCT-1026 may prove to be beneficial in preventing or delaying restenosis in humans.
 
The National Cholesterol Education Program’s Adult Treatment Panel III report (ATP III)1 identified the metabolic syndrome as a multiplex risk factor for cardiovascular disease (CVD) that is deserving of more clinical attention. Subsequently, the National Heart, Lung, and Blood Institute (NHLBI), in collaboration with the American Heart Association (AHA), convened a conference to examine scientific issues related to definition of the metabolic syndrome.2 The present report summarizes a second conference devoted to clinical management of the metabolic syndrome, which was sponsored by the AHA in partnership with the NHLBI and cosponsored by the American Diabetes Association (ADA). This latter conference considered the following issues: (1) pathogenesis and presentation of the metabolic syndrome, (2) management of underlying risk factors, (3) management of metabolic risk factors, and (4) unresolved issues and research challenges. The conference on definition2 confirmed CVD as a major clinical outcome of metabolic syndrome and identified 6 major components of the syndrome: abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, insulin resistance ± glucose intolerance, a proinflammatory state, and a prothrombotic state. The follow-up conference on management was structured around therapies for these components. Clinical recognition of the metabolic syndrome is generally based on finding several well-recognized signs in clinical practice: abdominal obesity, elevated triglycerides, reduced HDL cholesterol, raised blood pressure, and elevated plasma glucose. In addition, research shows that other components not routinely measured commonly aggregate with the major components: elevated apolipoprotein B, small LDL particles, insulin resistance and hyperinsulinemia, impaired glucose tolerance (IGT), elevated C-reactive protein (CRP), and variation in coagulation factors (eg, plasminogen activator inhibitor [PAI]-1 and fibrinogen). The conference on definition2 also emphasized that risk for type 2 diabetes is higher in persons with metabolic syndrome and that diabetes is a major risk factor for CVD. It also examined various criteria for …
 
To investigate whether chromosome 10q11.21 influences common carotid intima-media thickness (IMT) and atherosclerosis and whether it is associated with stromal cell-derived factor-1α (SDF-1α) plasma levels. Variation on chromosome 10q11.21 has been consistently associated with coronary artery disease. The genetic variant lies upstream of the gene encoding SDF-1α. We genotyped 3 population cohorts (Bruneck [age range, 45 to 94 years; 50.0% men; n=738], Health2000 [age range, 46 to 76 years; 55.4% men; n=1237], and essential hypertension in families collected in the region of Oxford [HTO] [age range, 19 to 88 years; 47.9% men; n=770]) for single-nucleotide polymorphism rs501120 at the 10q11.21 locus and conducted a meta-analysis in these cohorts to ascertain a relationship between the polymorphism and carotid IMT. The analysis showed that individuals with the T/T genotype had a significantly higher carotid IMT than individuals with the C/T or C/C genotype (pooled weighted mean difference, 23 μm [95% CI, 9 to 37 μm], P=0.0014 under a fixed-effects model; and 23 μm [95% CI, 6 to 41 μm], P=0.009 under a random-effects model). In the Bruneck cohort, in which data for carotid atherosclerosis and plasma SDF-1α levels were available, we observed an association of the T/T genotype with a higher burden of atherosclerosis and increased susceptibility to the development of atherosclerosis during a 5-year follow-up (multivariable odds ratio, 1.73 [95% CI, 1.18 to 2.52]; P=0.005 for the recessive model) and an association between the T/T genotype and lower SDF-1α levels (2.62 ng/mL for T/T versus 2.74 ng/mL for C/C or C/T; P=0.023). The coronary heart disease-related variant at the 10q11.21 locus is associated with carotid IMT and atherosclerosis.
 
Transforming growth factor-beta1 (TGF-beta1) controls the expression of numerous genes, including smooth muscle cell (SMC)-specific genes and extracellular matrix protein genes. Here we investigated whether c-Src plays a role in TGF-beta1 signaling in mouse embryonic fibroblast C3H10T1/2 cells. TGF-beta1 induction of the SMC contractile protein SM22alpha gene expression was inhibited by PP1 (an inhibitor of Src family kinases) or by C-terminal Src kinase (a negative regulator of c-Src). Induction of SM22alpha by TGF-beta1 was markedly attenuated in SYF cells (c-Src(-), Yes(-), and Fyn(-)) compared with Src(++) cells (c-Src(++), Yes(-), and Fyn(-)). PP1 also inhibited the TGF-beta1-induced expression of serum response factor (SRF), a transcription factor regulating the SMC marker gene expression. Confocal immunofluorescence analysis showed that TGF-beta1 stimulates production of hydrogen peroxide. Antioxidants such as catalase or NAD(P)H oxidase inhibitors such as apocynin inhibited the TGF-beta1-induced expression of SM22alpha. Furthermore, we demonstrate that TGF-beta1 induction of the plasminogen activator inhibitor-1 (PAI-1) gene, which is known to be dependent on Smad but not on SRF, is inhibited by PP1 and apocynin. Our results suggest that TGF-beta1 activates c-Src and generates hydrogen peroxide through NAD(P)H oxidase, and these signaling pathways lead to the activation of specific sets of genes, including SM22alpha and PAI-1. TGF-beta1 controls the expression of numerous genes, including SM22alpha and PAI-1. We investigated whether c-Src plays a role in TGF-beta1 signaling. TGF-beta1 induction of such genes was significantly reduced in Src family tyrosine kinase-deficient cells, and Csk and pharmacological inhibitors for Src family kinases or antioxidants inhibit the effects of TGF-beta1. These results indicate that c-Src and hydrogen peroxide are required for TGF-beta1 signaling.
 
Adherens junctions are symmetrical and elongated between collectivized smooth muscle cells (SMCs). A, Top, Electron micrographs of SMCs in medium with fetal bovine serum (FBS), showing adherens junctions with asymmetrical electron densities, and SMCs in medium without FBS, showing symmetrical adherens junctions (arrows). A, Bottom, Fluorescent micrographs of contacting SMCs immunostained with a pancadherin antibody and labeled with Texas-Red-X phalloidin and Hoechst 33258. For SMCs in 10% FBS (left), cadherins exist as short streaks near the ends of actin microfilament bundles. However, in serum-free media (right), cadherins are strikingly elongated. B, Box and whisker plot of median cadherin length, interquartile range, and 10th to 90th percentile range; n=358 and 297, cadherin aggregates for 10% and 0% FBS, respectively; *P<0.0001. Corresponding frequency distributions are on the right and indicate a right-shift in cadherin length for cells in the absence of serum.  
Calcium transients are coordinated among cadherin-11–dependent collectivized smooth muscle cells (SMCs). A, Spontaneous [Ca 2+ ] i oscillations in contacting SMCs cultured in the presence of 10% fetal bovine serum (FBS; noncollectivizing, short-duration adhesions) or 0% FBS (collectivizing, long-duration adhesions). Fluorescence ratios of fura-2–loaded SMCs are expressed relative to their respective baseline ratios at the start of the recording period and are plotted over time. Signals depicted are from the corresponding color-shaded cells in the fluorescent micrographs (images from 380-nm excitation). In FBS-supplemented media, independent oscillations are evident. Middle (0% FBS), Partial synchrony among the SMCs is seen. Right (0% FBS), SMCs display phase-locked synchrony of Ca 2+ oscillations. B, Graph depicting the proportion of coincidental [Ca 2+ ] i oscillations among contacting SMCs in the presence or absence of FBS; *P=0.0010. C, Fluorescent micrographs of contacting SMCs in 0% FBS that display propagation of [Ca 2+ ] i waves. The wave pathways are depicted by the yellow arrows and in the corresponding video files (Videos IV and V in the online-only Data Supplement ). Graphs below each micrograph chart depict the timing of the wavefront at a given location, establishing that the wave begins in the downstream SMC at the cell–cell contact site. D, Graphs depicting the influence of cadherin-11–blocking antibody, AF1790, and N-cadherin–blocking antibody, GC-4, on the percentage of coincident [Ca 2+ ] i transients between contacting SMCs under collectivizing culture conditions; *P=0.0428 and 0.037, respectively. E, Fluorescent micrographs of contacting SMCs and corresponding quantification of cell pairs with connexin 43 aggregates. Arrows indicate connexin 43 assemblies at cell–cell junctions (*P=0.0001). F, Graph depicting the effect of cadherin–blocking antibodies or respective control mouse (m) or goat (g) IgG on the proportion of cell pairs with connexin 43 aggregates (*P=0.0006, †P=0.0007, and † †P<0.0001 vs respective control IgG, † †P=0.049 vs SMCs incubated with GC-4).  
Smooth muscle cells (SMCs) in healthy arteries are arranged as a collective. However, in diseased arteries, SMCs commonly exist as individual cells, unconnected to each other. The purpose of this study was to elucidate the events that enable individualized SMCs to enter into a stable and interacting cell collective. Human SMCs stimulated to undergo programmed collectivization were tracked by time-lapse microscopy. We uncovered a switch in the behavior of contacting SMCs from semiautonomous motility to cell-cell adherence. Central to the cell-adherent phenotype was the formation of uniquely elongated adherens junctions, ≤60 μm in length, which appeared to strap adjacent SMCs to each other. Remarkably, these junctions contained both N-cadherin and cadherin-11. Ground-state depletion super-resolution microscopy revealed that these hybrid assemblies were comprised of 2 parallel nanotracks of each cadherin, separated by 50 nm. Blocking either N-cadherin or cadherin-11 inhibited collectivization. Cell-cell adhesion and adherens junction elongation were associated with reduced transforming growth factor-β signaling, and exogenous transforming growth factor-β1 suppressed junction elongation via the noncanonical p38 pathway. Imaging of fura-2-loaded SMCs revealed that SMC assemblies displayed coordinated calcium oscillations and cell-cell transmission of calcium waves which, together with increased connexin 43-containing junctions, depended on cadherin-11 and N-cadherin function. SMCs can self-organize, structurally and functionally, via transforming growth factor-β-p38-dependent adhesive switching and a novel adherens junction architecture comprised of hybrid nanotracks of cadherin-11 and N-cadherin. The findings define a mechanism for the assembly of SMCs into networks, a process that may be relevant to the stability and function of blood vessels. © 2015 American Heart Association, Inc.
 
Since the P(2T) purinergic (ADP) receptor is unique to the megakaryocytic/platelet lineage, cells of this lineage were screened for the relative effects of ADP and ATP in intracellular Ca2+ levels. Like platelets, CMK 11-5 cells responded with an increase in intracellular Ca2+ mobilization in response to ADP but not to ATP or adenosine. In contrast, both nucleotides increased intracellular Ca2+ mobilization in the megakaryoblastic cell lines MO7E and Meg-01, indicating that they contain P(2Y) receptors or a mixed complement of purinergic receptors. Pharmacological responsiveness of CMK 11-5 cells to nucleotides paralleled those of platelets, in which ADP and ADP-α-S are active as agonists and ATP and ATP-α-S are inactive as agonists but act as antagonists. [3H]ADP and 35S-ATP-α-S bound to CMK 11-5 cells at a high-affinity site (K(d1) and K(i1), 262 and 125 nmol/L, respectively) and a low-affinity site (K(d2) and K(i2), 10 100 and 5400 nmol/L, respectively) with 2 x 106 to 6 x 106 sites per cell. ADP bound at both sites was competed with ADP, ATP, and ATP-α-S with affinities in a rank order similar to that found for platelets (ATP-α- S≃ATP≃ADP≤ADP-β-S≃adenosine), suggesting the presence of a P(2T) receptor on CMK 11-5 cells. Photoaffinity labeling of intact CMK 11-5 cells with 35S-ATP-α-S resulted in the labeling of the α-subunit of GP IIb as found with platelets, although this was confirmed to be independent of ADP receptors. After RNA from CMK 11-5 cells was microinjected into Xenopus oocytes, only ADP and ADP-α-S stimulated 45Ca2+ efflux, which was not observed with ATP, 2-methylthio-ATP, α,β-methylene-ATP, ATP-γ-S, ATP-α- S, or adenosine. In addition, incubation of RNA-injected oocytes with ATP or ATP-α-S but not adenosine blocked the 45Ca2+ response to ADP. These experiments demonstrate that a nascent receptor that responded specifically to ADP but not to other P1, P(2Y), P(2X), and P(2U) agonists was expressed in functional form on Xenopus oocytes.
 
Scavenger receptor class B type I (SR-BI) is a multiligand cell-surface receptor that mediates the selective uptake of lipid from HDL cholesterol (HDL-C) into cells. This study hypothesized an association between functional variants in the promoter region of SR-BI gene and HDL-C levels. We identified 2 novel mutations in the SR-BI gene promoter region by using single-strand conformation polymorphism. One mutation was an 11-bp CCCCGCCCCGT deletion mutation from positions -140 to -150 relative to the transcription start site, corresponding to an Sp1 binding site; the other was a C-->T substitution at position -142. Twenty-six of 690 unrelated subjects were heterozygous for the -140 to -150 deletion mutation, and the allele frequency in this population was 0.02. This study showed that the deletion variant prevented binding of Sp1 to this region of the SR-BI promoter and effectively reduced transcriptional activities in HepG2 cells. Notably, the -140 to -150 deletion mutation was significantly associated with increased HDL-C levels and explained approximately 0.5% of the variation in HDL-C levels in this population. A genetic variant at the SR-BI gene promoter region might explain a significant proportion of individual differences in HDL-C levels among Taiwanese Chinese. Our results require further replication in an independent population.
 
11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes the intracellular reduction of inactive cortisone to active cortisol, the natural ligand activating the glucocorticoid receptor (GR). Peroxisome proliferator- activated receptor-γ (PPARγ) is a nuclear receptor controlling inflammation, lipid metabolism, and the macrophage polarization state. In this study, we investigated the impact of macrophage polarization on the expression and activity of 11β-HSD1 and the role of PPARγ therein. 11β-HSD1 gene expression is higher in proinflammatory M1 and anti-inflammatory M2 macrophages than in resting macrophages, whereas its activity is highest in M2 macrophages. Interestingly, PPARγ activation induces 11β-HSD1 enzyme activity in M2 macrophages but not in resting macrophages or M1 macrophages. Consequently, human M2 macrophages displayed enhanced responsiveness to the 11β-HSD1 substrate cortisone, an effect amplified by PPARγ induction of 11β-HSD1 activity, as illustrated by an increased expression of GR target genes. Our data identify a positive cross-talk between PPARγ and GR in human M2 macrophages via the induction of 11β-HSD1 expression and activity.
 
Progesterone and adipoQ receptor (PAQR) 10 and PAQR11 are 2 highly homologous genes involved in compartmentalized Ras signaling in the Golgi apparatus. The aim of this study was to investigate the physiological functions of PAQR10 and PAQR11. We used zebrafish as a model system to analyze the potential function of PAQR10/PAQR11. The expression profiles of PAQR10 and PAQR11 in zebrafish embryos are overlapping in many areas, but only PAQR11 is expressed in the developing heart. Knockdown of PAQR11 but not PAQR10 in zebrafish embryos causes cardiac developmental defects, including dilation of cardiac chambers, abnormal heart looping, disruption of atrioventricular cushion formation, heart edema, and blood regurgitation. PAQR11 knockdown markedly reduces the number and proliferation rate of cardiomyocytes and alters the morphology of myocardial cells during early heart development. The cardiac defects caused by PAQR11 knockdown can be phenocopied by MEK inhibitors and a dominant negative Ras. Furthermore, constitutively active Ras and especially a Golgi-localized but not a plasma membrane-localized Ras are able to rescue the cardiac defects caused by PAQR11 knockdown. This study not only provides in vivo evidence that PAQR11 plays a critical role in heart morphogenesis but also pinpoints the importance of compartmentalized Ras signaling during development.
 
Objective: Dystrophic calcific nodule formation in vitro involves differentiation of aortic valve interstitial cells (AVICs) into a myofibroblast phenotype. Interestingly, inhibition of the kinase MAPK Erk kinase (MEK)1/2 prevents calcific nodule formation despite leading to myofibroblast activation of AVICs, indicating the presence of an additional mechanotransductive component required for calcific nodule morphogenesis. In this study, we assess the role of transforming growth factor β1-induced cadherin-11 expression in calcific nodule formation. Methods and results: As shown previously, porcine AVICs treated with transforming growth factor β1 before cyclic strain exhibit increased myofibroblast activation and significant calcific nodule formation. In addition to an increase in contractile myofibroblast markers, transforming growth factor β1-treated AVICs exhibit significantly increased expression of cadherin-11. This expression is inhibited by the addition of U0126, a specific MEK1/2 inhibitor. The role of increased cadherin-11 is revealed through a wound assay, which demonstrates increased intercellular tension in transforming growth factor β1-treated AVICs possessing cadherin-11. Furthermore, when small interfering RNA is used to knockdown cadherin-11, calcific nodule formation is abrogated, indicating that robust cell-cell connections are necessary in generating tension for calcific nodule morphogenesis. Finally, we demonstrate enrichment of cadherin-11 in human calcified leaflets. Conclusions: These results indicate the necessity of cadherin-11 for dystrophic calcific nodule formation, which proceeds through an Erk1/2-dependent pathway.
 
The hypothesis that stromelysin-3 (MMP-11), a unique member of the matrix metalloproteinase (MMP) family, plays a role in neointima formation was tested with the use of a vascular injury model in wild-type (MMP-11(+/+)) and MMP-11-deficient (MMP-11(-/-)) mice. Neointima formation 2 to 3 weeks after electric injury of the femoral artery was significantly enhanced in MMP-11(-/-) as compared with MMP-11(+/+) mice, in both mice of a pure 129SV genetic background (0.014 versus 0.0010 mm(2) at 2 weeks, P<0.001) and those of a 50/50 mixed 129SV/BL6 background (0.030 versus 0.013 mm(2) at 3 weeks, P<0.05). The medial areas were comparable, resulting in intima/media ratios that were significantly increased in MMP-11(-/-) as compared with MMP-11(+/+) arteries, in mice of both the 129SV (1. 0 versus 0.18, P<0.001) and mixed (1.5 versus 0.70, P<0.05) backgrounds. Nuclear cell counts in cross-sectional areas of the intima of the injured region were higher in arteries from MMP-11(-/-) mice than in those from MMP-11(+/+) mice (210 versus 48, P<0.001, in pure 129SV mice and 290 versus 150, P<0.01, in mice of the mixed genetic background). Immunocytochemical analysis revealed that alpha-actin-positive and CD45-positive cells were more abundant in intimal sections of MMP-11(-/-) mice. Degradation of the internal elastic lamina was more extensive in arteries of MMP-11(-/-) mice than in those of MMP-11(+/+) mice (39% versus 6.8% at 3 weeks, P<0. 005). The mechanisms by which MMP-11 could impair elastin degradation and cellular migration in this model remain, however, unknown.
 
Collagen-binding integrins may be involved in controlling interstitial fluid pressure (Pif), transcapillary fluid flux, and tissue fluid volume. Our aim was to explore whether the newly discovered collagen binding alpha11beta1 integrin has a mechanistic role in inflammatory edema formation. In collagen matrices seeded with a mixture of mast cells and fibroblasts, fibroblasts lacking the alpha11 integrin subunit (alpha11(-/-)) contracted collagen gels less efficiently than control fibroblasts, suggesting that the alpha11beta1 integrin is able to mediate tensile force in connective tissues. In alpha11(-/-) mice, control Pif in skin did not differ from the pressure found in wild-type mice. Whereas a reduction in Pif was found in control mice after inducing inflammation, thereby contributing to fluid extravasation and edema formation, such a reduction was not seen in alpha11(-/-) mice. That this effect is mediated through the extracellular compartment is suggested by a similar plasma protein extravasation ratio in alpha11(-/-) and wild-type mice. Our data suggest that alpha11beta1 integrins on dermal fibroblasts mediate collagen lattice remodeling and have a mechanistic role in controlling Pif in inflammation and thereby fluid extravasation and edema formation in vivo.
 
The endothelial glycocalyx is composed of glycoproteins, proteoglycans, and glycosaminoglycans within a high-water-content meshwork overlying the endothelial cells lining blood vessels. This structure maintains the integrity of vascular permeability, protects endothelial cells against leukocytes and red blood cells, and regulates vascular flow and function.1,2 The preservation of the thickness of the glycocalyx is now thought to be an important aspect mediating vascular health; hence, a decrease in thickness may play a role in chronic vascular disease.3 Recently, there has been a discussion in the literature regarding the discrepancy of the glycocalyx measurements in vitro and in vivo.4 Most often, researchers have used traditional transmission electron microscopy (TEM) methods to preserve in vitro glycocalyx, resulting in measurements of less than 100 nm.5 By comparison, recent in vivo imaging studies have demonstrated a much thicker glycocalyx of 8.9 μm.6 To improve on the accuracy of in vitro measurement, researchers are now pursuing additional methodologies to better preserve the hydrated native and gel-like state of the glycocalyx. In this month's issue of Arteriosclerosis, Thrombosis, and Vascular Biology , Ebong et al7 present a cryofixation technique termed rapid freezing and freeze substitution (RF/FS) and report on the preservation and measurement of an 11-μm-thick glycocalyx. See accompanying article on page 1908 The cyrotechnique method used by Ebong et al7 is not new, as it was developed back in the 1950s for improved morphological and histochemical preservation of tissues examined by light microscopy.8 Rapid freezing is thought to …
 
Objective: Endothelial cell (EC) inflammatory status is critical to many vascular diseases. Emerging data demonstrate that mutations of Krüppel-like factor-11 (KLF11), a gene coding maturity-onset diabetes mellitus of the young type 7 (MODY7), contribute to the development of neonatal diabetes mellitus. However, the function of KLF11 in the cardiovascular system still remains to be uncovered. In this study, we aimed to investigate the role of KLF11 in vascular endothelial inflammation. Methods and results: KLF11 is highly expressed in vascular ECs and induced by proinflammatory stimuli. Adenovirus-mediated KLF11 overexpression inhibits expression of tumor necrosis factors-α-induced adhesion molecules. Moreover, small interfering RNA-mediated KLF11 knockdown augments the proinflammatory status in ECs. KLF11 inhibits promoter activity of adhesion molecules induced by tumor necrosis factor-α and nuclear factor-κB p65 overexpression. Mechanistically, KLF11 potently inhibits nuclear factor-κB signaling pathway via physical interaction with p65. Furthermore, KLF11 knockdown results in increased binding of p65 to vascular cell adhesion molecule-1 and E-selectin promoters. At the whole organism level, KLF11(-/-) mice exhibit a significant increase in leukocyte recruitment to ECs after lipopolysaccharide administration. Conclusions: Taken together, our data demonstrate for the first time that KLF11 is a suppressor of EC inflammatory activation, suggesting that KLF11 constitutes a novel potential molecular target for inhibition of vascular inflammatory diseases.
 
Objective: We demonstrated that inflammatory cells and intima-media thickening are increased in carotids exposed to low-blood flow in the SJL/J (SJL) strain compared with other mouse strains. We hypothesized that the extent of inflammation associated with intima-media thickening is a genetically regulated trait. Approach and results: We performed a whole genome approach to measure leukocyte infiltration in the carotid intima as a quantitative trait in a genetic cross between C3HeB/FeJ (C3H/F) and SJL mice. Immunostaining for CD45(+) (a pan-specific leukocyte marker) was performed on carotids from C3H/F, SJL, F1, and N2 progeny to measure leukocyte infiltration. We identified a nearly significant quantitative trait locus for CD45(+) on chromosome (chr) 11 (17 cM, LOD=2.3; significance was considered at threshold P=0.05). Interval mapping showed that the CD45(+) locus on chr 11 accounted for 8% of the variation in the logarithm of odds backcross. Importantly, the CD45(+) locus colocalized with the intima-modifier 2 (Im2) locus, which controls 17% of intima variation. We created 2 Im2 congenic lines of mice (C3H/F.SJL.11.1 and C3H/F.SJL.11.2) to better understand the regulation of intima-media thickening by the chr 11 locus. The C3H/F.SJL.11.1 congenic mouse showed ≈30% of the SJL trait, confirming that CD45(+) cell infiltration contributed to the intima trait. Conclusions: We discovered a novel locus on chr 11 that controls leukocyte infiltration in the carotid. Importantly, this locus overlaps with our previously published Im2 locus on chr 11. Our study reveals a potential mechanistic relationship between leukocyte infiltration and intima-media thickening in response to decreased blood flow.
 
The relationship between Chlamydia pneumoniae (Cpn) infection and arterial measures of preclinical atherosclerosis has remained controversial. Because atherogenesis begins in early life, we examined whether carotid and aortic intima-media thickness (IMT) and brachial artery endothelial function are associated with Cpn seropositivity in children. Cpn-specific IgG and IgA antibodies were assessed by enzyme immunoassay in 199 healthy children followed-up annually from 7 to 11 years of age. Carotid (cIMT) and aortic IMT (aIMT), and brachial artery flow-mediated dilatation (FMD) were measured in 137 of the 199 children at the age of 11 years using high-resolution ultrasound. Children with persistent IgG and/or IgA seropositivity to Cpn had significantly increased aIMT compared with seronegative children (IgG< or =45 and IgA< or =12 enzyme immunounits) or children with transient Cpn seropositivity (seronegative, 0.496 [0.054]; transient, 0.494 [0.061]; and persistent, 0.532 [0.086] mm; P<0.05 for trend). This trend was not explained by traditional atherosclerotic risk factors or pubertal stage. cIMT and FMD were not associated with Cpn seropositivity. Eleven-year-old children with persistent Cpn seropositivity show increased aIMT but not cIMT, suggesting that Cpn may affect the aortic wall, the site where the earliest atherosclerotic lesions are known to occur, in otherwise healthy children.
 
To investigate the role of recombinant human interleukin-11 (rhIL-11) on in vivo mobilization of CD34(+)/vascular endothelial growth factor receptor (VEGFR) 2(+) mononuclear cells and collateral vessel remodeling in a mouse model of hindlimb ischemia. We observed that treatment of Sv129 mice with continuous infusion of 200-μg/kg rhIL-11 per day led to in vivo mobilization of CD34(+)/VEGFR2(+) cells that peaked at 72 hours. Sv129 mice pretreated with rhIL-11 for 72 hours before femoral artery ligation showed a 3-fold increase in plantar vessel perfusion, leading to faster blood flow recovery; and a 20-fold increase in circulating CD34(+)/VEGFR2(+) cells after 8 days of rhIL-11 treatment. Histologically, experimental mice had a 3-fold increase in collateral vessel luminal diameter after 21 days of rhIL-11 treatment and a 4.4-fold influx of perivascular CD34(+)/VEGFR2(+) cells after 8 days of therapy. Functionally, rhIL-11-treated mice showed better hindlimb appearance and use scores when compared with syngeneic mice treated with PBS under the same experimental conditions. These novel findings show that rhIL-11 promotes in vivo mobilization of CD34(+)/VEGFR2(+) mononuclear cells, enhances collateral vessel growth, and increases recovery of perfusion after femoral artery ligation. Thus, rhIL-11 has a promising role for development as an adjunctive treatment of patients with peripheral vascular disease.
 
In this article, we studied the effect of acetyl-11-keto-beta-boswellic acid (AKbetaBA), a natural inhibitor of the proinflammatory transcription factor NF-kappaB on the development of atherosclerotic lesions in apolipoprotein E-deficient (apoE-/-) mice. Atherosclerotic lesions were induced by weekly LPS injection in apoE-/- mice. LPS alone increased atherosclerotic lesion size by approximately 100%, and treatment with AKbetaBA significantly reduced it by approximately 50%. Moreover, the activity of NF-kappaB was also reduced in the atherosclerotic plaques of LPS-injected apoE-/- mice treated with AKbetaBA. As a consequence, AKbetaBA treatment led to a significant downregulation of several NF-kappaB-dependent genes such as MCP-1, MCP-3, IL-1alpha, MIP-2, VEGF, and TF. By contrast, AKbetaBA did not affect the plasma concentrations of triglycerides, total cholesterol, antioxidized LDL antibodies, and various subsets of lymphocyte-derived cytokines. Moreover, AKbetaBA potently inhibited the IkappaB kinase (IKK) activity immunoprecipitated from LPS-stimulated mouse macrophages and mononuclear cells leading to decreased phosphorylation of IkappaB alpha and inhibition of p65/NF-kappaB activation. Comparable AKbetaBA-mediated inhibition was also observed in LPS-stimulated human macrophages. The inhibition of NF-kappaB activity by plant resins from species of the Boswellia family might represent an alternative for classical medicine treatments for chronic inflammatory diseases such as atherosclerosis.
 
We examined the relation between in vivo thrombogenicity and the morphology of carotid lesions to clarify the role of platelet deposition in carotid atherothrombosis. We evaluated 60 subjects (120 carotid bifurcations) who had at least one established risk factor for atherosclerosis by using indium 111 platelet scintigraphy and high-resolution B-mode ultrasonography. We evaluated platelet accumulation in the carotid arterial wall by means of a dual-tracer method that used In 111-labeled platelets and technetium 99m-labeled human serum albumin. The tracer accumulation was assessed both visually and semiquantitatively by using the platelet accumulation index, ie, the ratio of radioactivity of the amount of In 111-labeled platelets deposited on the vascular wall to the amount of radioactivity in labeled platelets circulating in the blood pool. The morphology of the carotid lesions was analyzed with B-mode ultrasonography in terms of the presence of ulceration, the maximum percent stenosis, the echogenicity of plaque, and the plaque score, which indicates the severity of systemic atherosclerosis. Platelet accumulation increased with increase in plaque score (P < .01), and the magnitude of platelet accumulation was significantly greater in lesions with ulceration than in those without (P < .05). The platelet accumulation index in vessels with plaque showed a very weak but significant correlation with maximum percent stenosis (r = .28, P < .05) and a stronger correlation with the unilateral plaque score (r = .42, P < .0001). Analysis of the echogenicity of plaque showed that heterogeneous plaque had a high frequency of accumulating platelets. Platelet accumulation was related to the surface characteristics and severity of carotid lesions, especially in the presence of ulceration.
 
The purpose of this study was to investigate the association of longitudinal change in serum gamma-glutamyltransferase (GGT) with mortality from cardiovascular disease (CVD). A population-based cohort of 76,113 Austrian men and women with 455,331 serial GGT measurements was prospectively followed-up for a median of 10.2 years after assessment of longitudinal GGT change during an average period of 6.9 years. Cox proportional hazards regression with time-varying covariates was used to evaluate GGT change as an independent predictor for CVD death. Independently of baseline GGT and other classical CVD risk factors, a pronounced increase in GGT (7-year change >9.2 U/L) was significantly associated with increased total CVD mortality in men (P=0.005); the adjusted hazard ratio (95% confidence interval) in comparison to stable GGT (7-year change -0.7 to 1.3 U/L) was 1.40 (1.09 to 1.81). Similarly, total CVD risk was elevated for increasing GGT in women, although effects were less pronounced and statistically significant only in subanalyses regarding coronary heart disease. Age of participants significantly modified the relation between GGT change and CVD mortality, with markedly stronger associations to be observable for younger individuals. Our study is the first to demonstrate that a longitudinal increase in GGT, independently of baseline GGT and even within its normal range, significantly increases risk of fatal CVD.
 
To the Editor: In a study of 395 men, Talmud and coworkers1 found a trend toward increased atherosclerosis progression in α1-antitrypsin deficiency S and Z carriers and a significantly increased atherosclerosis progression in α1-antitrypsin 11478A carriers compared with noncarriers. As opposed to this, recent studies suggest the opposite, a protective role of α1-antitrypsin deficiency against atherosclerotic disorders.2,3 In our study of 11,315 men and women, severe ZZ α1-antitrypsin deficiency and intermediate MZ deficiency were associated with reduced blood pressure, and MZ was also associated with reduced risk of ischemic cerebrovascular disease (ICVD) and ischemic heart disease (IHD).2 The MS genotype did not affect blood pressure or risk of IHD and ICVD in our study. We also screened subjects for the less severe 11478A variant in the α1-antitrypsin gene4 but never previously reported on risk of IHD and ICVD for this variant. Among men, odds ratios for IHD and ICVD in 11478A carriers versus noncarriers were 0.93 (0.76 to 1.1) and 0.98 (0.72 to 1.3). When these …
 
Although polymorphic variations in genes of the RAS system have previously been associated with susceptibility to AAA, such studies have been significantly limited by small sample sizes. This study was undertaken, using the largest case series yet reported, to determine whether common genetic variants of the RAS are associated with either susceptibility or severity of AAA. The frequencies of 4 common genetic variants of genes related to the renin-angiotensin system were investigated in 3 geographically distinct, but ethnically similar, case-control cohorts, resulting in comparison of 1226 AAA cases with 1723 controls. In all 3 the AGTR1 1166C allele was significantly more common in AAA patients than controls (overall adjusted OR 1.60, 95% CI 1.32 to 1.93, P=1.1x10(-6)). Overall, the ACE ID genotype was associated with AAA (OR 1.33, 95% CI 1.06 to 1.67, P<0.02). The AGT 268T allele appeared to have an epistatic effect on large aneurysm size. This study has identified a strong and repeated association between the AGTR1 1166C allele and susceptibility to AAA, and a weaker effect associated with the ACE deletion allele, in 3 geographically distinct, but ethnically similar, case-control cohorts. This study highlights the key role of the RAS in AAA and emphasizes the need for replication and validation of results in suitable independent cohorts.
 
The interaction of the heat shock protein 90 (Hsp90) with the endothelial NO synthase (eNOS) has been shown to account for a sustained production of NO in vitro. Here, we examined whether overexpression of Hsp90 in a pig model of cardiac infarct could preserve the myocardium from the deleterious effects of ischemia-reperfusion. Percutaneous liposome-based gene transfer was performed by retroinfusion of the anterior interventricular vein before left anterior descending occlusion and reperfusion. We found that recombinant Hsp90 expression in the ischemic region of the heart led to a 33% reduction in infarct size and prevented the increase in postischemic left ventricular end diastolic pressure observed in mock-transfected animals. Regional myocardial function, assessed by subendocardial segment shortening in the infarct region, was increased in Hsp90-transfected animals at baseline and after pacing. All these effects were completely abrogated by administration of the NOS inhibitor N(G)-nitro-L-arginine methyl ester. We further documented in vivo and in cultured endothelial cells that the cardioprotective effects of Hsp90 were associated to its capacity to act as an adaptor for both the kinase Akt and the phosphatase calcineurin, thereby promoting eNOS serine 1177 phosphorylation and threonine 495 dephosphorylation, respectively. Hsp90 is a promising target to enhance NO formation in vivo, which may efficiently reduce myocardial reperfusion injury.
 
Unlabelled: Background- Combined hyperlipidemia is a common disorder characterized by a highly atherogenic lipoprotein profile and increased risk of coronary heart disease. The etiology of the lipid abnormalities (increased serum cholesterol and triglyceride or either lipid alone) is unknown. Methods and results: We assembled 2 large cohorts of families with familial combined hyperlipidemia (FCHL) and performed disease and quantitative trait linkage analyses to evaluate the inheritance of the lipid abnormalities. Chromosomal regions 6q16.1-q16.3, 8p23.3-p22, and 11p14.1-q12.1 produced evidence for linkage to FCHL. Chromosomes 6 and 8 are newly identified candidate loci that may respectively contribute to the triglyceride (logarithm of odds [LOD], 1.43; P=0.005) and cholesterol (LOD, 2.2; P=0.0007) components of this condition. The data for chromosome 11 readily fulfil the guidelines required for a confirmed linkage. The causative alleles may contribute to the inheritance of the cholesterol (LOD, 2.04 at 35.2 cM; P=0.0011) component of FCHL as well as the triglyceride trait (LOD, 2.7 at 48.7 cM; P=0.0002). Conclusions: Genetic analyses identify 2 potentially new loci for FCHL and provide important positional information for cloning the genes within the chromosome 11p14.1-q12.1 interval that contributes to the lipid abnormalities of this highly atherogenic disorder.
 
15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), a natural ligand of the peroxisome proliferator-activated receptor-gamma (PPARgamma), has been shown to inhibit proinflammatory gene expression, but the signaling mechanisms involved remain unclear. Because retinoic acid receptor-related orphan receptor-alpha (RORalpha) has been reported to suppress tumor necrosis factor-alpha (TNF-alpha)-induced expression of proinflammatory genes, we hypothesized that 15d-PGJ2 may induce RORalpha expression resulting in inhibition of proinflammatory gene expression. We demonstrate that 15d-PGJ2 induced RORalpha1 and RORalpha4 expression and inhibited TNF-alpha-induced vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression in human umbilical vein endothelial cells (HUVECs). In contrast, the synthetic PPARgamma ligand pioglitazone weakly induced RORalpha4 expression but did not affect RORalpha1 expression or TNF-alpha-induced gene expression. Biphenol A diglycidyl ether, a PPARgamma antagonist, did not block the effect of 15d-PGJ2 on RORalpha expression. Adenovirus-mediated overexpression of RORalpha1 inhibited TNF-alpha-induced VCAM-1 and ICAM-1 expression, and overexpression of a mutant form of RORalpha1 (RORalpha1Delta), which inhibited transcriptional activity of RORalpha1 and RORalpha4, attenuated its inhibition. Furthermore, we found that RORalpha1Delta attenuated the inhibitory actions of 15d-PGJ2 on TNF-alpha-induced VCAM-1 and ICAM-1 expression. These results suggest that 15d-PGJ2 inhibits TNF-alpha-induced expression of proinflammatory genes mediated in part via induction of RORalpha in HUVECs. This mechanism provides a novel insight into PPARgamma-independent actions of 15d-PGJ2.
 
FK506 Binding Protein 12 and its related isoform 12.6 (FKBP12/12.6) stabilize a closed state of intracellular Ca2+ release channels (ryanodine receptors [RyRs]), and in myocytes removal of FKBP12/12.6 from RyRs alters intracellular Ca2+ levels. The immunosuppressive drugs rapamycin and FK506 bind and displace FKBP12/12.6 from RyRs, and can also cause endothelial dysfunction and hypertension. We tested whether rapamycin and FK506 cause an intracellular Ca2+ leak in endothelial cells and whether this affects endothelial function and blood pressure regulation. Rapamycin or FK506 concentration-dependently caused a Ca2+ leak in isolated endothelial cells, decreased aortic NO production and endothelium-dependent dilation, and increased systolic blood pressure in control mice. Rapamycin or FK506 at 10 micromol/L abolished aortic NO production and endothelium-dependent dilation. Similar results were obtained in isolated endothelial cells and aortas from FKBP12.6-/- mice after displacement of FKBP12 with 1 micromol/L rapamycin or FK506. In hypertensive FKBP12.6-/- mice, systolic blood pressures were further elevated after treatment with either rapamycin or FK506. Blockade of the Ca2+ leak with ryanodine normalized NO production and endothelium-dependent dilation. Complete removal of FKBP12 and 12.6 from endothelial RyRs induces an intracellular Ca2+ leak which may contribute to the pathogenesis of endothelial dysfunction and hypertension caused by rapamycin or FK506.
 
A protein that specifically binds oxidized LDL (Ox-LDL) has recently been characterized in mouse peritoneal macrophages and identified as macrosialin, a protein with a molecular weight of 95 kD. First, the present work shows that human monocyte-derived macrophages express a membrane protein with a molecular weight of approximately 120 kD that selectively binds Ox-LDL. Second, we tested whether this approximately 120-kD Ox-LDL binding protein had any relation to CD68, the human homologue of macrosialin. The following evidence was obtained to support the role of CD68 as an Ox-LDL binding protein: (1) Ligand blots with Ox-LDL and Western blots with Ki-M6, an anti-human CD68 monoclonal antibody, revealed a single band with a molecular weight of approximately 120 kD under reducing and nonreducing condition. (2) The expression patterns of the approximately 120-kD Ox-LDL binding membrane protein and of CD68 paralleled each other during monocyte/macrophage differentiation. (3) Digestion with N-glycosidase F demonstrated that both CD68 and the Ox-LDL binding protein are glycoproteins; both showed a similar shift of approximately 18 kD in apparent molecular weight. (4) CD68, probed with monoclonal antibody Ki-M6, and the approximately 120-kD Ox-LDL binding protein were coprecipitated with EMB11, another anti-CD68 antibody. About 5000 molecules of CD68 are expressed on the cell surface of human macrophages. Ligation of 125I-Ki-M6 to cells leads to its internalization and degradation. This capacity would be sufficient to allow for the specific uptake and degradation of Ox-LDL. Taken together, these data support a role for CD68 as a specific Ox-LDL binding protein in human monocyte-derived macrophages.
 
Ferritin concentrations are often increased in patients with metabolic syndrome and type 2 diabetes mellitus, but few reports have examined the associations between ferritin and atherosclerosis. We investigated whether any relationship between ferritin and coronary artery calcium score (CACS) >0 (as a marker of atherosclerosis) was independent of potential confounders, such as iron-binding capacity (transferrin), low-grade inflammation, and cardiovascular risk factors. Data were analyzed from a South Korean occupational cohort of 12 033 men who underwent a cardiac computed tomography estimation of CACS and measurements of multiple cardiovascular risk factors. One-thousand three- hundred-fifteen of 12 033 (11.2%) subjects had a CACS >0. For people with a CACS >0, median (interquartile range) ferritin concentration was 196.8 (136.3-291.9) compared with 182.2 (128.1-253.6) in people with a CACS=0; P<0.001. In the highest ferritin quartile, 14.7% (442/3008) of subjects had a CACS >0 compared with 9.7% (292/3010) in the lowest quartile (P<0.0001). With increasing ferritin quartiles, there were also higher proportions of people with diabetes mellitus (P<0.0001), hypertension (P<0.0001), coronary heart disease (P=0.003), and a Framingham Risk Score >10% (P<0.0001). In logistic regression modeling with CACS >0 as the outcome, ferritin but not transferrin was independently associated with CACS >0 (odds ratio for highest quartile versus lowest quartile, 1.66 [95% CI, 1.3-1.98]; P=0.0001). Increased ferritin concentrations are associated with the presence of a marker of early coronary artery atherosclerosis, independently of traditional cardiovascular risk factors including Framingham risk score, transferrin, preexisting vascular disease, diabetes mellitus, metabolic syndrome factors, and low-grade inflammation.
 
Vascular endothelial growth factor receptor(VEGFR)-3 is a critical regulator of developmental and adult vasculogenesis and lymphangiogenesis through its interactions with select members of the VEGF family. The goal of this study was to investigate how VEGFR-3 expression is regulated during inflammatory lymphangiogenesis. In this study, we present for the first time evidence that VEGFR-3 can be negatively regulated by a mirtron, hsa-miR-1236 (miR-1236), which is expressed in primary human lymphatic endothelial cells. In human lymphatic endothelial cells, miR-1236 is upregulated in response to IL-1β, a negative regulator of VEGFR-3. miR-1236 binds the 3' untranslated region of Vegfr3, resulting in translational inhibition. Overexpression of miR-1236 significantly decreased expression of VEGFR-3, but not VEGFR-2, in human lymphatic endothelial cells. Compared to a control miR, overexpression of miR-1236 also led to decreased VEGFR-3 signaling. However, VEGFR-2-specific signaling was not affected. miR-1236 can attenuate human lymphatic endothelial cell migration and tube formation, as well as in vivo lymphangiogenesis. Our data suggest that miR-1236 may function as a negative regulator of VEGFR-3 signaling during inflammatory lymphangiogenesis.
 
MicroRNA plays important roles in vascular biology, but the regulation of endothelial-specific microRNA is not well characterized. MicroRNA-126 (miR-126) is highly expressed in endothelial cells, and it regulates angiogenesis and vascular inflammation. Here we show that the transcription factors Ets-1 and Ets-2 regulate miR-126 expression. A genomic region between -71 and -100 bp upstream of the miR-126 transcriptional start site is critical for transactivation of the gene containing miR-126. This genomic region contains a potential Ets binding site. Mutations within the Ets binding site block transactivation, and Ets-1 and Ets-2 interact with this critical genomic region. Knockdown of endogenous Ets-1 and Ets-2 decreases miR-126 expression. Finally, knockdown of miR-126 alters regulation of an Ets-1 target gene. Taken together, these data show that the transcription factors Ets-1 and Ets-2 play a key role in controlling the expression of miR-126 and suggest that miR-126 may mediate some of their vascular effects.
 
Atherosclerosis is a condition caused by lipid-induced inflammation of the vessel wall orchestrated by a complex interplay of various cell types, such as endothelial cells , smooth muscle cells , and macrophages. MicroRNAs (miRNAs) have emerged as key regulators of gene expression typically by repressing the target mRNA, which determines cell fate and function under homeostatic and disease conditions. Here, we outline the effects of miRNA-145, -126, and -155 in atherosclerosis in vivo. Downregulation of miR-145, which controls differentiation of smooth muscle cells, promotes lesion formation, whereas the endothelial cell-specific miRNA-126 signals the need for endothelial repair through its transfer from apoptotic endothelial cells in microvesicles. Elevated miR-155 levels are characteristic of proinflammatory macrophages and atherosclerotic lesions. However, the effects of miR-155 seem to be different in early and advanced atherosclerosis. The discovery of the role of these miRNAs in atherosclerosis sheds light on the current concepts of atherogenesis and may provide novel treatment options for cardiovascular diseases.
 
MicroRNAs (miRs) are small noncoding RNAs that post-transcriptionally control gene expression by binding to target mRNAs and thereby inducing translational inhibition or mRNA degradation. Most primary miRs are endogenously processed by endonucleases such as Drosha, and the resulting pre-miRs are then cleaved by an enzyme called Dicer to form ≈22-nucleotide duplexes. One strand of the duplex, the guide strand, is preferentially selected for entry in the silencing complex by argonaute-2, whereas the other strand, known as passenger strand or miRNA* strand, is typically degraded. However, in many cases, both strands are biologically active as miRs. In that case, both distinct mature miRs arise from the same pre-miR and are referred to as 5p and 3p (Figure). Figure. Shear stress induces microRNA (miR)-126-5p, which provides atheroprotection via the inhibition of Delta-like 1 homolog (Dlk1). After processing by Dicer, miR-126-5p and miR-126-3p are loaded into RNA-induced silencing complexes. Through a mechanism yet unknown, specifically miR-126-5p levels are induced after cells are exposed to laminar shear stress. miR-126-5p inhibits the expression of Dlk1, an antiproliferative inhibitor of Notch, leading to enhanced endothelial proliferation and atheroprotection. VCAM 1 indicates vascular cell adhesion molecule 1. Several miRs control the function of …
 
The C57BL/6 (B6) and 129 mouse inbred strains differ markedly in plasma HDL-cholesterol concentrations and atherosclerosis susceptibility after a high-fat diet consumption. To identify loci controlling these traits, we performed quantitative trait loci (QTL) analysis. We fed a high-fat diet to 294 (B6x129S1/SvImJ)F2 females for 14 weeks, measured plasma HDL concentrations and size of aortic fatty-streak lesions, genotyped F2 females, and performed QTL analysis. HDL concentrations were affected by six loci: Hdlq14 and Hdlq15 on chromosome 1 (peaks cM 80 and cM 104, logarithm of odds [LOD] 5.3 and 9.7, respectively); Hdlq16 on chromosome 8 (cM 44, LOD 2.6); Hdlq17 on chromosome 9 (cM 24, LOD 2.9); Hdlq18 on chromosome 12 (cM 20, LOD 5.9); and Hdlq19 on chromosome 2 (cM 90), which interacted with Hdlq15. Atherosclerosis susceptibility was affected by five loci: Ath17 on chromosome 10 (cM 34, LOD 6.6); Ath18 on chromosome 12 (cM 16, LOD 3.7); Ath19 (chromosome 11, cM 60), which interacted with Ath18; and Ath20 (chromosome 10, cM 10), which interacted with Ath21 (chromosome 12, cM 50). We identified six loci for HDL and five loci for atherosclerosis susceptibility in a (B6x129S1/SvImJ)F2 intercross.
 
Interleukin-12 is essential for the differentiation of naïve T cells into interferon-γ-producing T cells, which regulate inflammatory responses. We investigated this process of regulating hypertension-induced cardiac fibrosis. Mice infused with angiotensin II showed a marked increase in interleukin-12p35 expression in cardiac macrophages. The degree of cardiac fibrosis was significantly enhanced in interleukin-12p35 knockout (p35-KO) mice compared with wild-type (WT) littermates in response to angiotensin II. Fibrotic hearts of p35-KO mice showed increased accumulation of alternatively activated (M2) macrophages and expression of M2 genes such as Arg-1 and Fizz1. Bone marrow-derived macrophages from WT or p35-KO mice did not differ in differentiation in response to angiotensin II treatment; however, in the presence of CD4(+) T cells, macrophages from p35-KO mice differentiated into M2 macrophages and showed elevated expression of transforming growth factor-β. Moreover, CD4(+) T-cell-treated p35-KO macrophages could stimulate cardiac fibroblasts to differentiate into α-smooth muscle actin-positive and collagen I-positive myofibroblasts in 3-dimensional nanofiber gels. Neutralizing antibodies against transforming growth factor-β inhibited myofibroblast formation induced by M2 macrophages. Deficiency in interleukin-12p35 regulates angiotensin II-induced cardiac fibrosis by promoting CD4(+) T-cell-dependent differentiation of M2 macrophages and production of transforming growth factor-β.
 
Oxidized free fatty acids have profound effects on cultured cells. However, little is known about whether these effects depend on their uptake and metabolism by cells or primarily involve their interaction with cell-surface components. We determined the uptake and metabolism of unoxidized (linoleic or oleic acid) and oxidized linoleic acid (13-hydroperoxyoctadecadienoic acid, 13-HPODE) by endothelial cells, smooth muscle cells, and macrophages. We show that 13-HPODE is poorly taken up by cells. The levels of uptake were dependent on the cell type but were independent of the expression of CD36. 13-HPODE was also poorly used by microsomal lysophosphatidylcholine acyltransferase that is involved in the formation of phosphatidylcholine. Based on these results, we suggest that most of the biological effects of 13-HPODE and other oxidized free fatty acids on cells might involve a direct interaction with cell-surface components. Alternatively, very small amounts of oxidized free fatty acids that enter the cell may have effects, analogous to those of hormones or prostanoids.
 
Oxidatively modified low density lipoprotein (LDL) has been implicated in the pathogenesis of atherosclerosis. LDL oxidation may be mediated by several factors, including cellular lipoxygenases. The lipoxygenase product of linoleic acid, 13-hydroperoxyoctadecadienoic acid (13-HPODE), is a significant component of oxidized LDL and has been shown to be present in atherosclerotic lesions. However, the mechanism of action of these oxidized lipids in vascular smooth muscle cells (VSMCs) is not clear. In the present study, we show that 13-HPODE leads to the activation of Ras as well as the mitogen-activated protein kinases, extracellular signal-regulated kinase 1/2, p38, and c-Jun amino-terminal kinase, in porcine VSMCs. 13-HPODE also specifically activated the oxidant stress-responsive transcription factor, nuclear factor-kappaB, but not activator protein-1 or activator protein-2. 13-HPODE-induced nuclear factor-kappaB DNA binding activity was blocked by an antioxidant, N-acetylcysteine, as well as an inhibitor of protein kinase C. 13-HPODE, but not the hydroxy product, 13-(S)-hydroxyoctadecadienoic acid, also dose-dependently increased vascular cell adhesion molecule-1 promoter activation. This was inhibited by an antioxidant as well as by inhibitors of Ras p38 mitogen-activated protein kinase and protein kinase C. Our results suggest that oxidized lipid components of oxidized LDL, such as 13-HPODE, may play a key role in the atherogenic process by inducing the transcriptional regulation of inflammatory genes in VSMCs via the activation of key signaling kinases.
 
To better understand the role of lecithin:cholesterol acyltransferase (LCAT) in lipoprotein metabolism through the genetic and biochemical characterization of families carrying mutations in the LCAT gene. Thirteen families carrying 17 different mutations in the LCAT gene were identified by Lipid Clinics and Departments of Nephrology throughout Italy. DNA analysis of 82 family members identified 15 carriers of 2 mutant LCAT alleles, 11 with familial LCAT deficiency (FLD) and 4 with fish-eye disease (FED). Forty-four individuals carried 1 mutant LCAT allele, and 23 had a normal genotype. Plasma unesterified cholesterol, unesterified/total cholesterol ratio, triglycerides, very-low-density lipoprotein cholesterol, and pre-beta high-density lipoprotein (LDL) were elevated, and high-density lipoprotein (HDL) cholesterol, apolipoprotein A-I, apolipoprotein A-II, apolipoprotein B, LpA-I, LpA-I:A-II, cholesterol esterification rate, LCAT activity and concentration, and LDL and HDL3 particle size were reduced in a gene-dose-dependent manner in carriers of mutant LCAT alleles. No differences were found in the lipid/lipoprotein profile of FLD and FED cases, except for higher plasma unesterified cholesterol and unesterified/total cholesterol ratio in the former. In a large series of subjects carrying mutations in the LCAT gene, the inheritance of a mutated LCAT genotype causes a gene-dose-dependent alteration in the plasma lipid/lipoprotein profile, which is remarkably similar between subjects classified as FLD or FED.
 
Lack of endothelial nitric oxide synthase worsens atherosclerosis at least by increasing monocyte adhesion to endothelial cells. The purpose of this study was to elucidate the molecular mechanism elicited by NO. We evaluated atherosclerosis in apoE and NOS3/apoE-deficient mice fed with high-cholesterol diet. We found significant increase in aortic lesion size, and infiltration of macrophages in NOS3/apoE-null mice when compared to apoE-deficient animals. To test the relevance of cellular adhesion as well as extracellular matrix degradation, we evaluated ICAM-1, VCAM-1, PECAM-1, MMP-2, MMP-9, MMP-12, MT1-MMP, and MMP-13 levels in mouse aortas. Lack of NO inhibits MMP-13 and increases ICAM-1 levels in atherosclerosis as compared to apoE-null mice. Ectopically expression of ICAM-1 in eukaryotic cells revealed that extracellular domain of ICAM-1 harbors a substrate recognized by MMP-13. Incubation of COS-7 cells expressing ectopic ICAM-1 in the presence of active MMP-13 induced inhibition of RAW 264.7 cell adhesion to COS-7 monolayers. MALDI-TOF MS analysis combined to Liquid chromatography coupled to Ion Trap MS on ICAM-1 incubated with MMP-13 allowed us to determine the cleavage sites of MMP-13 at positions E61 and G98 of ICAM-1. G98 is part of a PDGQS moiety, which shows homology with the consensus PDGLS substrate located at the MMP-13 cleaved site of type II collagen I-alpha. Taking together, these results point toward MMP-13 as a mechanism for the NO-mediated protection of atherosclerosis.
 
Substantial evidence implicates interstitial collagenases of the matrix metalloproteinase (MMP) family in plaque rupture and fatal thrombosis. Understanding the compensatory mechanisms that may influence the expression of these enzymes and their functions, therefore, has important clinical implications. This study assessed in mice the unknown relative effect of the 2 principal collagenases on collagen content and other plaque characteristics. Apolipoprotein E-deficient (apoE(-/-)) mice, MMP-13(-/-) apoE(-/-), MMP-8(-/-) apoE(-/-) double knockout mice, and MMP-13(-/-) MMP-8(-/-) apoE(-/-) triple knockout mice consumed a high-cholesterol diet for 10 and 24 weeks. Both double knockout and triple knockout mice showed comparable atherosclerotic lesion formation compared with apoE(-/-) controls. Analysis of aortic root sections indicated that lesions of MMP-8/MMP-13-deficient and MMP-13-deficient mice accumulate more fibrillar collagen than apoE(-/-) controls and MMP-8(-/-) apoE(-/-) double knockout. We further tested the relative effect of MMPs on plaque collagenolysis using in situ zymography. MMP-13 deletion alone abrogated collagenolytic activity in lesions, indicating a predominant role for MMP-13 in this process. MMP-13 and MMP-13/MMP-8 deficiency did not alter macrophage content but associated with reduced accumulation of smooth muscle cells. These results show that among MMP interstitial collagenases in mice, MMP-13 prevails over MMP-8 in collagen degradation in atheromata. These findings provide a rationale for the identification and selective targeting a predominant collagenase for modulating key aspects of plaque structure considered critical in clinical complications, although they do not translate directly to human lesions, which also contain MMP-1.
 
Top-cited authors
Renu Virmani
  • George Washington University
James I. Cleeman
  • Agency for Healthcare Research and Quality
Sidney Smith
  • University of North Carolina at Chapel Hill
Frank D Kolodgie
  • Czech Metrology Institute
William S Harris
  • University of South Dakota