Nonatherosclerotic Coronary Arteries Research Articles

PAR4 Inhibition Reduces Coronary Artery Atherosclerosis and Myocardial Fibrosis in SR-B1/LDLR Double Knockout Mice.

SR-B1 (scavenger receptor class B type 1)/LDLR (low-density lipoprotein receptor) double knockout mice fed a high-fat, high-cholesterol diet containing cholate exhibit coronary artery disease characterized by occlusive coronary artery atherosclerosis, platelet accumulation in coronary arteries, and myocardial fibrosis. Platelets are involved in atherosclerosis development, and PAR (protease-activated receptor) 4 has a prominent role in platelet function in mice. However, the role of PAR4 on coronary artery disease in mice has not been tested. We tested the effects of a PAR4 inhibitory pepducin (RAG8) on diet-induced aortic sinus and coronary artery atherosclerosis, platelet accumulation in atherosclerotic coronary arteries, and myocardial fibrosis in SR-B1/LDLR double knockout mice. SR-B1/LDLR double knockout mice were fed a high-fat, high-cholesterol diet containing cholate and injected daily with 20 mg/kg of either the RAG8 pepducin or a control reverse-sequence pepducin (SRQ8) for 20 days. Platelets from the RAG8-treated mice exhibited reduced thrombin and PAR4 agonist peptide-mediated activation compared with those from control SRQ8-treated mice when tested ex vivo. Although aortic sinus atherosclerosis levels did not differ, RAG8-treated mice exhibited reduced coronary artery atherosclerosis, reduced platelet accumulation in atherosclerotic coronary arteries, and reduced myocardial fibrosis. These protective effects were not accompanied by changes in circulating lipids, inflammatory cytokines, or immune cells. However, RAG8-treated mice exhibited reduced VCAM-1 (vascular cell adhesion molecule 1) protein levels in nonatherosclerotic coronary artery cross sections and reduced leukocyte accumulation in atherosclerotic coronary artery cross sections compared with those from SRQ8-treated mice. The PAR4 inhibitory RAG8 pepducin reduced coronary artery atherosclerosis and myocardial fibrosis in SR-B1/LDLR double knockout mice fed a high-fat, high-cholesterol diet containing cholate. Furthermore, RAG8 reduced VCAM-1 in nonatherosclerotic coronary arteries and reduced leukocyte and platelet accumulation in atherosclerotic coronary arteries. These findings identify PAR4 as an attractive target in reducing coronary artery disease development, and the use of RAG8 may potentially be beneficial in cardiovascular disease.

Myocardial infarction in a 33-year-old with inflammatory bowel disease: a case report

BackgroundST elevation myocardial infarction is defined as acute myocardial injury with necrosis due to myocardial ischemia. The frequent cause is thrombotic occlusion of atherosclerotic coronary arteries. In particular situations, thromboembolism can cause myocardial infarction in patients with normal coronary arteries.Case presentationWe report a particular case of myocardial infarction in a young, previously healthy patient with non-atherosclerotic coronary arteries and inflammatory bowel disease. Although we performed an extensive work up, no clear pathophysiological cause could be diagnosed. Most likely, myocardial infarction was associated with a hypercoagulative state related to systemic inflammation.ConclusionThe mechanisms of coagulation disturbances in the context of acute and chronic inflammation are not yet fully understood. A better understanding of cardiovascular events in patients with inflammatory bowel disease might lead to new treatment approaches of cardiovascular disease.

CHARACTERISTICS OF THE CORONARY ARTERIAL LESIONS IN YOUNG PATIENTS WITH ACUTE MYOCARDIAL INFARCTION

ABSTRACT OBJECTIVES: To assess characteristics of coronary arterial lesion (CAL) by means of invasive coronary angiography in young patients, aged <35 years, who sustained acute myocardial infarction (AMI).METHODS: This prospective study of one-year duration was conducted from December 2009 to November 2010 at the cardiology departments of three teaching hospitals in Peshawar, Pakistan. All patients aged <35 years, evaluated angiographically after an AMI, were included. The individual CAL were characterized.RESULTS: About 101 patients with AMI underwent coronary angiography. Mean age of the patients was 32.56±3.26 years (range 22–35 years). Out of 101 patients, 86 (78.18%) were males, while 15 (21.81%) were females. On coronary angiography, there were 25 (24.8%) patients with non-atherosclerotic coronary arteries, 39 (38.6%) with single vessel disease (SVD), 18 (17.8%) had double vessel disease (DVD), and 19 (18.8%) had triple vessel disease (TVD). Of the total, 3 patients (2.97%) had disease in the left main stem. One hundred thirty-two lesions (39x1=39 in SVD; 18x2=36 in DVD & 19x3=57 in TVD) were studied. The lesions were mostly discrete to tubular with less diffuse involvement and had either no or mild calcification. Thrombus was found in 5 patients with SVD (12.82%), 2 with DVD (11.11%) and 1 with TVD (1.75%).CONCLUSION: This study shows that young (age <35 years) patients who have sustained AMI, have less extensive coronary artery disease but complex morphologic features. There was a higher incidence of normal vessels on coronary angiography with a very few cases of left main coronary arterial involvement.KEY WORDS: Myocardial Infarction (MeSH); Coronary Artery Disease (MeSH); Coronary arterial lesions (Non-MeSH); Coronary Angiography (MeSH), Atherosclerosis (MeSH)

Sudden coronary death in the young: Evidence of contractile phenotype of smooth muscle cells in the culprit atherosclerotic plaque

Culprit coronary atherosclerotic plaques (APs) from young sudden cardiac death (SCD) victims are mostly non-atheromatous, i.e., consisting of proliferative smooth muscle cells (SMCs). Coronary vasospasm has been advocated to explain plaque instability in the absence of thrombosis. Our aim was to characterize the SMC phenotype in the intima and media of coronary arteries from young SCD victims. A total of 38 coronary artery segments were studied: (a) 18 APs from young (≤40 years old) SCD patients, (b) 9 APs from old (>40 years old) SCD patients, (c) 11 non-atherosclerotic coronary arteries from young patients (≤40 years old). Markers of differentiated SMCs such as α-smooth muscle actin (α-SMA), smooth muscle myosin heavy chains (SMMHCs), and heavy-caldesmon (h-CaD), were assessed in intima and media by immunohistochemistry and quantified morphometrically. In the intima, their expression was higher in non-atherosclerotic arteries (44.37 ± 3.03% for α-SMA, 14.21 ± 2.01% for SMMHCs, 8.90 ± 1.33% for h-CaD) and APs from young SCD victims (38.95 ± 2.29% for α-SMA, 11.92 ± 1.92% for SMMHCs, 8.93 ± 1.12% for h-CaD) compared with old patients (22.01 ± 3.56% for α-SMA, 6.39 ± 0.7% for SMMHCs, 3.00 ± 0.57% for h-CaD; all P statistically significant). The media of non-atherosclerotic arteries and APs from young SCD victims exhibited strong positivity for the differentiation markers unlike that of old patients. SMCs of coronary APs as well as from the underlying media from young SCD victims exhibit strong contractile phenotype. In the setting of critical stenosis, both intima and media SMC contractility might contribute to transient coronary spasm leading to myocardial ischemia and SCD.

PTEN deficiency promotes pathological vascular remodeling of human coronary arteries.

Phosphatase and tensin homolog (PTEN) is an essential regulator of the differentiated vascular smooth muscle cell (SMC) phenotype. Our goal was to establish that PTEN loss promotes SMC dedifferentiation and pathological vascular remodeling in human atherosclerotic coronary arteries and nonatherosclerotic coronary arteries exposed to continuous-flow left ventricular assist devices (CF-LVADs). Arteries were categorized as nonatherosclerotic hyperplasia (NAH), atherosclerotic hyperplasia (AH), or complex plaque (CP). NAH coronary arteries from CF-LVAD patients were compared to NAH coronaries from non-LVAD patients. Intimal PTEN and SMC contractile protein expression was reduced compared with the media in arteries with NAH, AH, or CP. Compared with NAH, PTEN and SMC contractile protein expression was reduced in the media and intima of arteries with AH and CP. NAH arteries from CF-LVAD patients showed marked vascular remodeling and reduced PTEN and α-smooth muscle actin (αSMA) in medial SMCs compared with arteries from non-LVAD patients; this correlated with increased medial collagen deposition. Mechanistically, compared with ApoE–/– mice, SMC-specific PTEN-null/ApoE–/– double-knockout mice exhibited accelerated atherosclerosis progression and increased vascular fibrosis. By microarray and validated quantitative RT-PCR analysis, SMC PTEN deficiency promotes a global upregulation of proinflammatory and profibrotic genes. We propose that PTEN is an antiinflammatory, antifibrotic target that functions to maintain SMC differentiation. SMC loss of PTEN results in pathological vascular remodeling of human arteries.

CHARACTERISTICS OF THE CORONARY ARTERIAL LESIONS IN YOUNG PATIENTS (< 35YEARS) WITH ACUTE MYOCARDIAL INFARCTION

Objective: This study was designed to assess characteristics of coronary arteriallesion by means of invasive coronary angiography in young patients, less than age35 years, who sustained acute myocardial infarction. Methodology: This prospective study was conducted from December 2009 toNovember 2010 at the cardiology departments of all the three tertiary care hospitalsin Peshawar. Total duration of the study was one year. All patients aged <35 yearswho were evaluated angiographically after an acute myocardial infarction wereincluded. The individual coronary arterial lesions were characterized. Result: A total of 101 patients with acute myocardial infarction underwentcoronary angiography. Mean age of the patients was 32.56±3.26 years (range 22- 35 years). About eighty-six patients (78.18%) were males. As revealed by thecoronary angiography, there were 25 (24.8%) patients with non-atheroscleroticcoronary arteries, 39 (38.6%) with single vessel disease, 18 patients (17.8%) haddouble vessel disease, and 19 patients (18.8%) had triple vessel disease.Of thetotal, 3 patients (2.97%) had disease in the left main stem. As far as the length of thelesions is concerned, the lesions were mostly discrete to tubular with less diffuseinvolvement.The lesions mostly either had no or mild calcification. Thrombus wasfound in 5 patients with SVD (12.82%), 2 patients with DVD (11.11%) and 1 patientwith TVD(1.75%).These lesions were located mostly in the ostial to proximalsegments, and were mostly severely to completely occlusive disease. Type Alesions were found in 14%, type B1 in 33%, type B2 in 27%, type C1 in 25%, andtype C2 in none. Conclusion: We found that young (age < 35 years) patients who havemyocardial infarction, have less extensive coronary artery disease but complexmorphologic features, with a high incidence of angiographically normal vessels andrelative paucity of left main coronary arterial involvement. Key Words: Acute Myocardial infarction, Coronary arterial lesions, Coronaryangiography.

Assessment of vascular response to BiOSS LIM C® stents vs Orsiro® stents in the porcine coronary artery model.

The optimal treatment strategy for coronary bifurcation lesions is still unknown. The aim of the study was to assess applicability of the new cobalt-chromium version of the sirolimus-eluting dedicated bifurcation BiOSS® LIM C stent in comparison with regular sirolimus-eluting Orsiro® stent in a porcine coronary model. A total of 13 BiOSS® LIM C stents and 6 Orsiro® stents were implanted in normal nonatherosclerotic porcine straight coronary arteries of six animals using 1.2:1.0 stent-to-artery ratio. Stent geometry and morphology were evaluated by Faxitron imaging. Vascular response was assessed by quantitative coronary angiography (QCA), optical coherence tomography (OCT), and histological analyses. OCT performed at 28days confirmed that all stents were patent with no signs of thrombus. In morphometric analysis, no differences between groups regarding stent diameter (P=.141), neointima area (P=.247), % area stenosis (P=.293), or % diameter stenosis (P=.069) were observed. Also, no significant differences were noted between groups regarding their histopathology scores. The injury and inflammation scores were low (mean grade<1) in all groups. The novel BiOSS® LIM C stent demonstrates good short-term vascular effects in a porcine coronary bifurcation model which are comparable with Orsiro® stents.

Myocardial Infarction in a Premenopausal Woman on Leuprolide Therapy.

Premenopausal women with chest pain syndrome may have nonatherosclerotic coronary arteries with abnormal coronary flow. Estrogens have cardioprotective effect improving coronary vasodilatation. This case report discusses the consequences of leuprolide use by decreasing estrogen levels which led to acute myocardial infarction.

Expression of MMP-15 and MMP-24 in atherosclerotic and nonatherosclerotic coronary arteries

Expression of MMP-15 and MMP-24 in atherosclerotic and nonatherosclerotic coronary arteries

Lumen Gain and Restoration of Pulsatility After Implantation of a Bioresorbable Vascular Scaffold in Porcine Coronary Arteries

Using intravascular ultrasound (IVUS) and histomorphometry, this study sought to evaluate the potential of nonatherosclerotic porcine coronary arteries to undergo progressive lumen gain and a return of pulsatility after implantation with an everolimus-eluting bioresorbable vascular scaffold (BVS). Unique benefits such as lumen gain and restored vasomotion have been demonstrated clinically after treatment with BVS; however, a more rigorous demonstration of these benefits with a randomized clinical trial has not yet been conducted. Seventy nonatherosclerotic swine received 109 everolimus-eluting BVS and 70 everolimus-eluting metal stents randomized among the main coronary arteries. Arteries were evaluated in vivo by angiography and IVUS and post-mortem by histomorphometry at time points from 1 to 42 months. From 1 to 6 months, both BVS- and everolimus-eluting metal stent-implanted arteries demonstrated stable lumen areas (LAs). From 12 months to 42 months, there was a progressive increase in the LA of arteries implanted with a BVS as assessed by histomorphometry and IVUS. This lumen gain in the implanted segment corresponded to an increase in the reference vessel LA. Normalization in the in-segment LA (LA:reference vessel LA) was observed qualitatively by angiography and quantitatively by IVUS. Additionally, BVS-implanted arteries demonstrated restored in-segment pulsatility on the basis of IVUS assessment of the differences in the mid-scaffold area between end-diastole to end-systole. Starting at 12 months, BVS-implanted porcine coronary arteries underwent progressive lumen gain and showed restored pulsatility. These benefits demonstrated preclinically may translate into improvements in long-term clinical outcomes for patients treated with BVS compared with conventional drug-eluting stents.

Measurement of Circumferential Strain Distribution in Human Coronary Arteries with Atherosclerotic Plaque

Rupture of atherosclerotic plaque in coronary artery causes serious results. Since heterogeneously distributed plaque may cause local stress concentration, the local strain in circumferential direction of the coronary artery with atherosclerosis was investigated. For eight specimens from four human atherosclerotic coronary arteries, four needles were stuck into each the specimen at equal intervals on their circumference. Specimens were pressurized and local circumferential length was calculated from movement of the needles observed from longitudinal direction. For each specimen, pressure strain elastic modulus Ep, stiffness parameter β, and incremental elastic modulus Einc were calculated. Local circumferential strain was calculated by referring to circumferential length at no-stress state. Total thickness Ttotal, plaque thickness Tplaque, medial and adventitial wall thickness Twall, and area fraction of plaque Aplaque were also measured in histological sections. Ep and β obtained in the present study were almost comparable to those of nonatherosclerotic human coronary arteries in previous studies. Local strains were different even in a circumference. The local strain at 80 mmHg ε80 correlated significantly with Twall (r = 0.48, p < 0.05), while ε80 had insignificant correlation with Tplaque, Ttotal, and Aplaque. Coefficient of variance of local Twall decreased with the increase in the pressure. These results indicate that mechanical properties of human atherosclerotic coronary arteries are heterogeneously distributed in circumferential direction, plaque has insignificant effect to their mechanical properties, and Twall becomes more uniform at physiological state than at no-stress state. These dada may be useful to simulate stress distribution in atherosclerotic coronary artery.

Do Pharmacokinetics Explain Persistent Restenosis Inhibition by a Single Dose of Paclitaxel?

The purpose of this study was to investigate the elimination of paclitaxel from the arterial wall after a single short administration with a coated balloon. Slightly oversized paclitaxel-coated balloons (dose 3 or 9 μg/mm(2)) without or with premounted stents were inflated in nonatherosclerotic coronary arteries of either young domestic pigs or adult Goettingen minipigs. The paclitaxel content of plasma, arterial segments, and residual hearts (without treated arteries) was measured for up to 180 days using high-performance liquid chromatography/ultraviolet detection or mass spectrometry. Angiograms were evaluated for lumen narrowing. The paclitaxel concentration in plasma remained <10 ng/mL. In arteries of domestic pigs and minipigs treated with paclitaxel-coated balloons with premounted stents, 10%±5% or 21%±8% of dose, respectively, was initially detected and decreased to 3.5%±3.1% of dose (domestic pig) by Day 7. Within 6 months it fell with a half-life of 1.9 months to 0.40%±0.35%. After 3 months the concentration in the arterial wall was 17±11 μmol/L. Without a stent, drug transfer to the vessel wall was somewhat reduced and elimination faster. Immediately after treatment up to 26%±4% of dose was detected in the residual whole hearts. It dropped with a half-life of 45 days to 1.5%±0.6% of dose (0.3 μmol/L) within 6 months. After a single local administration with coated balloons, paclitaxel stays in the vessel wall of pigs long enough to explain persistent inhibition of neointimal proliferation. The pharmacokinetics of paclitaxel does, however, not exclude other reasons for sustained efficacy such as early blocking of processes initiating excessive and prolonged neointimal proliferation.

Vascular Responses to Drug-Eluting and Bare Metal Stents in Diabetic/Hypercholesterolemic and Nonatherosclerotic Porcine Coronary Arteries

Animal models used to gain insight into the vascular response to drug-eluting stents are generally juvenile and nonatherosclerotic, whereas stents are placed in patients with complex atherosclerosis and comorbidities. Hence, models reflecting these complexities are needed to help elucidate the vascular effects of drug-eluting stents. We compared the vascular responses with bare metal stent (BMS) and paclitaxel-eluting stent (PES) implantation in a diabetic/hypercholesterolemic (DM/HC) porcine model of advanced coronary atherosclerosis with the standard juvenile porcine model. Two studies using similar stent procedural protocols were performed in either DM/HC (n=20) or domestic swine (non-DM/HC, n=20). Animals pretreated with dual-antiplatelet therapy, underwent BMS or PES implantation (1/artery, 2 stents per animal) and were euthanized 30 or 90 days later. DM/HC resulted in a 24% increase in platelet aggregation (P=0.05 versus baseline), whereas dual-antiplatelet therapy reduced platelet aggregation in both groups (P<0.0001). DM/HC pigs developed substantially greater neointimal area versus non-DM/HC pigs, regardless of stent type, (P=0.004 for BMS at 30 days and P=0.002 at 90 days, P=0.005 for PES at 30 days, P=0.002 at 90 days). Compared with non-DM/HC pigs, reendothelialization was delayed in DM/HC pigs, more so after PES implantation. Increased para-strut leukocytes were observed for PES compared with BMS in the DM/HC pigs at both 30 days (P=0.023) and 90 days (P=0.04). As well, increased T-lymphocyte infiltration was seen in the DM/HC pigs. Stent implantation in a DM/HC swine model provides a metabolic environment closer to human disease, including hyperglycemia, hypercholesterolemia, and increased platelet aggregation. This model augmented differences in the vascular response between PES and BMS that are not as clearly evident in the non-DM/HC swine, including increased neointimal area, delayed reendothelialization, and greater, persistent vascular inflammation.

Time Course of Reendothelialization of Stents in a Normal Coronary Swine Model

Late thrombosis of coronary drug-eluting stents is an infrequent but serious complication of percutaneous transluminal coronary angioplasty. The best predictor of this event is the lack of endothelialization of stent struts. The objective of this study is to characterize and quantify the time course of endothelialization of different stents implanted in nonatherosclerotic swine coronary arteries. Thirty-three Carbofilm-coated stents were implanted percutaneously in 11 anesthetized domestic, crossbred pigs (weight 25 ± 3 kg, 2 months old). Each animal received 1 stainless steel stent (SS), 1 cobalt-chromium stent (CCS), and 1 tacrolimus-eluting stent (TES) in each coronary artery. Follow-up periods were 1 day (n = 9 stents), 3 days (n = 9 stents), and 7 days (n = 15 stents). Longitudinal sections of the stented vessels were examined using scanning electron microscopy. At 1 day, there was scarce, patchy endothelialization with areas of fibrin; the endothelialization rate was similar for all the stents (SS, 29% ± 23%; CCS, 29% ± 24%; TES, 31% ± 25%; P = .9). At 3 days, there were more endothelial cells but with immature features and giant cells over fibrin; the endothelialization was greater in SS and CCS than in TES (SS, 79% ± 14%; CCS, 81% ± 17%; TES, 46% ± 9%; P = .007). At 7 days, arteries showed better endothelialization with few giant cells; the endothelialization was greater in SS and CCS than in TES (SS, 95% ± 4%; CCS, 98% ± 4%; TES, 79% ± 9%; P = .01). In conclusion, the described model is useful for the analysis of endothelialization of coronary stents and facilitates measurement of its rate of formation and characterization of the involved cell types.

Enhanced expression of TLR4 in smooth muscle cells in human atherosclerotic coronary arteries

Toll-like receptors (TLRs) play an essential role in innate immunity as components of the primary defense system against microbial infections. It has become evident that TLRs are also involved in the pathogenesis of various cardiovascular diseases. However, the expression patterns of TLRs in the human coronary arteries of coronary artery disease (CAD) patients and the regulatory mechanisms of their expression remain unknown. The TLR4 expression patterns were invstigated by immunohistochemical analysis of coronary specimens obtained from autopsy cases or CAD patients by using directional coronary atherectomy. In atherosclerotic coronary arteries (n = 8), TLR4 immunoreactivity was colocalized with infiltrating inflammatory cells. Interestingly, vascular smooth muscle cells of atherosclerotic coronary arteries intensely expressed TLR4 even in the regions that had few inflammatory cells. In contrast, TLR4 expression was barely detected in the vascular smooth muscle cells of nonatherosclerotic coronary arteries (n = 4). Furthermore, intense expression of smooth muscle TLR4 was observed in the coronary arteries of CAD patients (n = 52). Stimulation with tumor necrosis factor alpha and angiotensin II increased the expression of TLR4 mRNA in cultured human vascular smooth muscle cells. Candesartan, an antagonist of the angiotensin II type 1 receptor (AT1), and N-acetylcystine inhibited angiotensin II-induced TLR4 mRNA expression in these cells. These findings suggest that the vascular smooth muscle cells of atherosclerotic coronary arteries may be activated to express TLR4. Furthermore, proinflammatory cytokines and oxidative stress in the inflammatory lesions might contribute to the enhanced expression of TLR4 in vascular smooth muscle cells of atherosclerotic arteries.

Expression, localisation and function of ACE and chymase in normal and atherosclerotic human coronary arteries

The expression, localisation and function of enzymes responsible for the local formation of angiotensin II in atherosclerotic and non-atherosclerotic human coronary arteries were studied. Human epicardial coronary arteries expressed mRNA for both ACE and chymase. Immunohistochemical studies revealed that ACE was localised to the vascular endothelium, and to a lesser extent the medial smooth muscle cells, in both large and small arteries. Chymase was detected in both types of vessel but was shown to be associated with mast cells. The contractions to angiotensin I in large arteries were inhibited only by a combination of quinaprilat and soyabean trypsin inhibitor. In the intramyocardial arteries the response to angiotensin I was markedly inhibited in the presence of chymostatin. These findings demonstrate that a dual pathway for the synthesis of angiotensin II is active in diseased and non-diseased coronary arteries.

Identification of new genes differentially expressed in coronary artery disease by expression profiling.

Genetic factors increase the risk to coronary artery disease (CAD). To date, a limited number of genes that potentially contribute to development of CAD have been identified. In this study, we have performed large-scale gene expression analysis of approximately 12,000 human genes in nine severely atherosclerotic and six nonatherosclerotic human coronary arteries using oligonucleotide microarrays. Fifty-six genes showed differential expression in atherosclerotic coronary artery tissues; expression of 55 genes was increased in atherosclerotic coronary arteries, whereas only one gene, GST, encoding a reducing agent, showed downregulated expression. The expression data of selected genes were validated by quantitative RT-PCR analysis as well as immunostaining. The associations of 49 genes with CAD appear to be novel, and they include genes encoding ICAM-2, PIM-2, ECGF1, fusin, B cell activator (BL34, GOS8), Rho GTPase activating protein-4, retinoic acid receptor responder, beta2-arrestin, membrane aminopeptidase, cathepsins K and H, MIR-7, TNF-alpha-induced protein 2 (B94), and flavocytochrome 558. In conclusion, we have identified 56 genes whose expression is associated with CAD, and 49 of them may represent new genes linked to CAD.

Cell-associated and extracellular phospholipid transfer protein in human coronary atherosclerosis.

Phospholipid transfer protein (PLTP) plays an important role in HDL particle metabolism and may modulate hepatic secretion of apolipoprotein B-containing lipoproteins. However, whether PLTP might participate directly in human atherosclerotic lesion formation is unknown. The cellular and extracellular distributions of PLTP were determined in normal and atherosclerotic human coronary lesions with a monoclonal antibody to human PLTP. Cell types (smooth muscle cells [SMCs] or macrophages), apolipoproteins (apoA-I, apoB, and apoE), and extracellular matrix proteoglycans (biglycan and versican) were identified on adjacent sections with monospecific antibodies. Minimal extracellular PLTP was detected in nonatherosclerotic coronary arteries, but extracellular and cellular PLTP immunostaining was widespread in atherosclerotic lesions. PLTP was detected in foam cell SMCs and in foam cell macrophages, which suggests that cellular cholesterol accumulation might increase PLTP expression in both cell types. This was confirmed by in vitro studies demonstrating that cholesterol loading of macrophages leads to 2- to 3-fold increases in PLTP steady-state mRNA levels, protein expression, and activity. PLTP also was detected in an extracellular distribution, colocalizing with apoA-I, apoB, apoE, and the vascular proteoglycan biglycan. In gel mobility shift assays, both active and inactive recombinant PLTP markedly increased HDL binding to biglycan, which suggests that PLTP may mediate lipoprotein binding to proteoglycans independent of its phospholipid transfer activity. PLTP is present in human atherosclerotic lesions, and its distribution suggests roles for PLTP in both cellular cholesterol metabolism and lipoprotein retention on extracellular matrix.

Immunohistochemical localization of endothelial cell-derived lipase in atherosclerotic human coronary arteries.

A novel lipoprotein lipase (LPL)-like gene, endothelial cell-derived lipase (EDL), was recently cloned from vascular endothelial cells. The presence of LPL in the vascular wall has been implicated in the progression of atherosclerosis through the bridging function between lipoprotein particles and matrix proteoglycans to enhance lipoprotein uptake into the vascular wall. The aim of this study was to investigate the local expression of EDL in human coronary arteries. Human coronary arterial specimens from 10 autopsied cases were examined by immunohistochemistry with polyclonal antibodies against specific synthetic EDL peptides. Immunohistochemical analysis revealed that EDL was expressed in endothelial cells and medial smooth muscle cells in non-atherosclerotic coronary arteries. In addition, EDL was expressed in infiltrating cells within atheromatous plaques as well as endothelial and smooth muscle cells. Double labeling immunofluorescence confirmed EDL positive-cells were endothelial cells, smooth muscle cells and macrophages. EDL immunoreactivity was also detected in neovasculature within atheromatous plaques in atherosclerotic coronary arteries. These results suggest that EDL may have unique functional roles in the pathogenesis of coronary artery diseases such as atherosclerosis as well as in lipid metabolism in the vessel wall.

Haptoglobin elutes from human atherosclerotic coronary arteries—a potential marker of arterial pathology

Molecules which egress from atherosclerotic arteries may function as plasma markers of arterial pathology, but such egress has not been proven with living human coronary arteries. We hypothesised that proteins eluting from the arterial wall may discriminate between atherosclerotic and non-atherosclerotic coronary arteries. During cardiac bypass surgery, 155 sequential fractions of antegradely flushed coronary cardioplegia solution were collected by balloon-cuffed catheter from the coronary sinus in subjects with angiographically extensive (n=30) or minor (n=7) coronary disease. Although plasma was the major source of protein in heavily blood-contaminated samples, under conditions of low blood contamination (<0.5 mg/ml red cell Haemoglobin) coronary circulation-derived protein was detected. N-terminal sequencing of a major 40 kDa band detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated 100% homology with beta chain of Haptoglobin (Hpt). Comparison of perfusates from patients with and without significant coronary disease found that the concentration of Hpt was markedly increased in perfusates from atherosclerotic coronary arteries (0.099+/-0.017 microg Hpt/microg Hb) relative to controls (0.016+/-0.008 microg Hpt/microg Hb, P=0.0027). Analysis of peripheral plasma samples of the same subjects, and of a separate cohort of patients, confirmed greater Hpt in those with angiographic coronary disease than in those without disease. Proteins such as Hpt elute from the human coronary vascular bed and may differentiate between arteries with minor or extensive atherosclerosis. Although the suitability of Hpt as a circulating plasma marker for atherosclerosis remains to be established, the approach used in the present study may permit identification of diverse plasma-detectable markers of atherosclerosis, and the subsequent non-invasive evaluation of in vivo arterial pathology.