Mechanisms of plaque vulnerability and rupture

Polarization-sensitive optical coherence tomography for imaging human atherosclerosis

Polarization-sensitive optical coherence tomography (PS-OCT) combines the advantages of OCT with image contrast enhancement, which is based on its ability to detect phase retardation and the fast-axis angle. Both PS-OCT images and histopathology have demonstrated similar features that allowed differentiation of atherosclerotic structures (i.e., plaques) from normal tissue. Moreover, the picrosirius polarization method was used to confirm PS-OCT assessment of collagen in the fibrous cap of atherosclerotic plaques, and high-frequency (40 MHz) ultrasound images were used to identify calcium in the vessel wall. Our preliminary ex vivo investigation of human aortic specimens indicated that PS-OCT might help to identify atherosclerotic lesions.

Perivascular mast cells promote atherogenesis and induce plaque destabilization in apolipoprotein E-deficient mice

BACKGROUND

Mast cells are major effector cells in allergy and host defense responses. Their increased number and state of activation in perivascular tissue during atherosclerosis may point to a role in cardiovascular disorders. In the present study, we investigated the contribution of perivascular mast cells to atherogenesis and plaque stability in apolipoprotein E-deficient mice.

METHODS AND RESULTS

We show here that episodes of systemic mast cell activation during plaque progression in mice leads to robust plaque expansion. Targeted activation of perivascular mast cells in advanced plaques sharply increases the incidence of intraplaque hemorrhage, macrophage apoptosis, vascular leakage, and CXCR2/VLA-4-mediated recruitment of leukocytes to the plaque. Importantly, treatment with the mast cell stabilizer cromolyn does prevent all the adverse phenomena elicited by mast cell activation.

CONCLUSIONS

This is the first study to demonstrate that mast cells play a crucial role in plaque progression and destabilization in vivo. We propose that mast cell stabilization could be a new therapeutic approach to the prevention of acute coronary syndromes.

Relationships between free radical levels during carotid endarterectomy and markers of arteriosclerotic disease

BACKGROUND

Free radical production is elevated in jugular venous blood emerging from the brain in conjunction with carotid endarterectomy. This study explores the relationships between markers for lesion progression in arteriosclerosis, production of radicals and clinical characteristics.

METHODS

The radical production during carotid endarterectomy was studied in 13 patients with an ex vivo spin trap method using OXANOH as a spin trap. MCP-1, ICAM-1, MMP-9 and oxLDL were determined in venous blood samples before, during and after clamping of the carotid artery. Principal component analysis (PCA) as well as partial least square regression analysis (PLS) was applied to interpret the data.

RESULTS

PCA and PLS analysis revealed that high values of MMP-9 and low values of ICAM-1 were associated with high radical production whereas MCP-1 and oxLDL were not correlated to radical production. MMP-9 was elevated at diabetes, high haemoglobin, high leucocyte counts and thrombocyte counts as well as at contralateral stenosis, whereas ICAM-1 showed reversed relationships to these clinical variables. MCP-1 increased during surgery.

CONCLUSIONS

The main finding in our study is that MMP-9 in plasma is asscociated with radical production during carotid endarterectomy, suggesting that this enzyme might be involved in the pathogenesis of brain damage in conjunction with ischaemia-reperfusion.

MRI of atherosclerosis: diagnosis and monitoring therapy

Atherosclerosis is a prevalent disease affecting millions of Americans. Despite our advances in diagnosis and treatment, atherosclerosis is the leading cause of death in America. High-resolution magnetic resonance imaging has overcome the limitations of current angiographic techniques and has emerged as a leading noninvasive imaging modality for atherosclerotic disease. Atherosclerosis of the arterial wall of the human carotid, aortic, peripheral and coronary arteries have all been successfully evaluated. In addition, the power of magnetic resonance imaging to differentiate the major components of atherosclerotic plaque has been validated. The ability to image the vessel wall and risk stratify atherosclerotic plaque will create management decisions not previously faced, and has the potential to change the way atherosclerosis is treated.

Plaque Composition in the Left Main Stem Mimics the Distal But Not the Proximal Tract of the Left Coronary Artery

OBJECTIVES

We sought to investigate whether plaques located in the left main stem (LMS) differ in terms of necrotic core content from those sited in the proximal tract of the left coronary artery.

BACKGROUND

Plaque composition, favoring propensity to vulnerability, might be nonuniformly distributed along the vessel, which might explain the greater likelihood for plaque erosion or rupture to occur in the proximal but not in the distal tracts of the coronary artery or in LMS.

METHODS

A total of 72 patients were included prospectively; 48 (32 men; mean age 57 +/- 11 years; 25 with stable angina and 23 affected by acute coronary syndromes) underwent a satisfactory nonculprit vessel investigation through spectral analysis of intravascular ultrasound radiofrequency data (IVUS-Virtual Histology, Volcano Corp., Rancho Cordova, California). The region of interest was subsequently divided into LMS and LMS carina, followed by 6 consecutive nonoverlapping 6-mm segments in left anterior descending artery in 34 patients or in circumflex artery in 14 patients.

RESULTS

Necrotic core content (%): 1) was minimal in LMS (median [interquartile range]: 4.6 [2 to 7]), peaked in the first 6-mm coronary segment (11.8 [8 to 16]; p < 0.01), and then progressively decreased distally; 2) was overall greater in patients with acute coronary syndromes (11.4 [5.5 to 19.8]) than stable angina (7.3 [3.2 to 12.9]; p < 0.001); 3) was largely independent from plaque size; and 4) did not correlate to systemic levels of C-reactive protein or lipid profile.

CONCLUSIONS

Plaques located in the LMS carry minimal necrotic content. Thus, they mimic the distal but not the proximal tract of the left coronary artery, where plaque rupture or vessel occlusion occurs more frequently.

Calcification of coronary intima and media: immunohistochemistry, backscatter imaging, and x-ray analysis in renal and nonrenal patients

Coronary calcification is a potent predictor of cardiac events. In patients with chronic renal disease, both prevalence and intensity of coronary calcification are increased. It has remained uncertain whether it is the intima of the coronaries or the media that is calcified and whether the morphologic details of calcified plaques differ between renal and nonrenal patients. Autopsy samples of coronaries were obtained from standard sites in 23 renal and 23 age- and gender-matched nonuremic patients. Specimens were examined using light and electron microscopy, immunohistochemistry, backscatter imaging, and x-ray analysis. In coronaries, calcified plaques occupied a similar proportion of the intima area in renal versus nonrenal patients (17.3 +/- 11.9 versus 18.1 +/- 11.9%) but occupied a significantly higher proportion of the media (16.6 +/- 10.6 versus 3.8 +/- 2.31%). Expression of the proteins osteocalcin, C-reactive protein, TGF-beta, and collagen IV was significantly more intensive around coronary plaques of renal compared with nonrenal patients. The non-plaque-bearing intima of renal patients showed minimal staining for fetuin, but fetuin staining was seen surrounding calcified plaques. In addition, more pronounced deposition of C5b-9 was found around coronary plaques of renal patients, and glycophorin deposition pointed to more past intraplaque hemorrhage in renal patients. Calcification by electron backscatter analysis is more intense in the coronary media, but not if the intima is more intense in renal compared with nonrenal patients. A more marked inflammatory response in renal patients is suggested by more frequent presence and greater intensity of markers of inflammation.

Regression of coronary artery outward remodeling in patients with non-ST-segment acute coronary syndromes: a longitudinal study using noninvasive magnetic resonance imaging

BACKGROUND

The association of plaques with outward arterial remodeling and acute coronary syndromes (ACS) has been mostly investigated by cross-sectional intravascular ultrasound studies. Magnetic resonance imaging (MRI) has made it possible to noninvasively assess the coronary vessels of patients with chronic coronary artery disease, but no study has been done in patients with ACS. We sought to serially investigate changes in coronary vessel walls of patients with ACS using noninvasive serial MRI.

METHODS

A total of 42 segments of coronary arteries from 22 patients presenting with non-ST-segment elevation ACS were studied at baseline in the acute phase and at 6 months after stabilization and optimization of medical therapy. Patients received routine medical treatment during this period with control of risk factors. Vessel wall area, maximum wall thickness, mean wall thickness, and lumen area were analyzed longitudinally using MRI.

RESULTS

Vessel wall area (38.8 +/- 20.0 vs 27.7 +/- 10.4 mm2; P = .001), maximum wall thickness (2.9 +/- 0.7 vs 2.5 +/- 0.6 mm; P < .001), and mean wall thickness (2.0 +/- 0.7 vs 1.6 +/- 0.5 mm; P < .001) were significantly reduced at 6 months compared with baseline, whereas lumen area did not show significant changes (11.5 +/- 4.8 vs 10.9 +/- 5.0 mm2; P = .52). The wall/lumen ratio was significantly reduced from 3.7 +/- 1.7 to 2.9 +/- 1.3 (P = .01), suggesting a regression of outward remodeling.

CONCLUSION

Patients with ACS have increased coronary vessel wall thickness and area that can regress with stabilization and medical therapy over the period of 6 months. Magnetic resonance imaging can detect and serially follow these changes, monitoring coronary vascular remodeling from the acute to the chronic phase of the disease.

Lipid cartography of atherosclerotic plaque by cluster-TOF-SIMS imaging

Several frozen vessels bearing atherosclerotic lesion were analysed by cluster TOF-SIMS (time-of-flight secondary ion mass spectrometry) to map their lipid (fatty acids, cholesterol, vitamin E, phosphatidic acids, phosphatidylinositols and triglycerides) content at a micrometric resolution.

Biomarkers of atherosclerotic plaque instability and rupture

Basic research over the last two decades has identified a large number of molecules pertinent to the atherosclerotic process, which have clearly improved our understanding of the underlying pathology. It is now well established that inflammation represents a major feature which is present in the vessel wall throughout all stages of the disease until the final pathophysiologic steps, representing plaque destabilization and eventually plaque rupture. Several cells typical for the atherosclerotic plaque, like monocyte-derived macrophages and T-lymphocytes are able to produce and secrete such mediator molecules, like cytokines, chemokines, growth-factors, enzymes, and disintegrins, which lead to activation of endothelial cells, proliferation of smooth muscle cells, lesion progression, and finally to the weakening of a vulnerable plaque by matrix degradation of its fibrous cap. Today, many of these molecules involved can be measured systemically by sensitive assays, and elevated concentrations in the circulation have been shown to be associated with future cardiovascular events. Determination of several of these molecules carries important prognostic information, independent of traditional risk factors, and may turn out to be useful in improving risk stratification. However, for most of these biomarkers the clinical utility has not yet been established.

What are the most useful and trustworthy noninvasive anatomic markers of existing vascular disease?

Cardiovascular disease is the leading cause of mortality and morbidity in developed countries. Evidence challenges the notion that the severity of lesions on angiography is a predictor of future cardiac events. With the recognition that subclinical coronary artery stenoses are responsible for myocardial infarcts and sudden death, it may be important to identify patients with plaque characteristics that may place them at increased risk. Intravascular ultrasound, though invasive, remains the current imaging gold standard. Computed tomography, cardiac magnetic resonance, and single-photon emission CT positron emission tomography are evolving and promising modalities. Functional studies reflecting plaque temperature and molecular imaging reflecting plaque constituents are being developed. We review the pathology of the vulnerable atherosclerotic plaque and recent innovations in imaging modalities to assess plaque complication risk.

Serial angiography in patients with acute coronary syndromes: effect of antithrombotic therapy on angiographic lesion severity

BACKGROUND

Patients presenting with acute coronary syndromes (ACS) commonly have a responsible culprit coronary lesion. There is limited data on the natural history of this culprit lesion in the short term and whether there is a change in morphology of this lesion in the days following presentation. Furthermore, the effect of antithrombotic therapy on this process is unknown.

METHODS

Sixty-eight patients presenting with ACS had their diagnostic study performed at our institution and had coronary angioplasty performed a few days later at a different hospital. Culprit lesion characteristics including minimum luminal diameter (MLD) and percentage diameter stenosis were determined on each occasion.

RESULTS

Acute myocardial infarction patients (n=14) had improved culprit lesion characteristics at angioplasty compared to baseline (diameter stenosis 78.9% versus 62.4%, p<0.01). Similarly, patients presenting with unstable angina (UA) or non-ST elevation myocardial infarction (non-STEMI) (n=54) had improved diameter stenosis (78.0% versus 72.7%, p<0.001). The change in MLD was greater in MI patients than UAP/non-STEMI patients (0.6mm versus 0.16mm, p<0.01).

CONCLUSION

Treatment of ACS patients with aspirin with anticoagulant therapy followed by delayed intervention results in angiographic improvement in lesion severity which may provide a more favourable environment in which to undertake percutaneous coronary intervention.

Elemental composition, morphology and mechanical properties of calcified deposits obtained from abdominal aortic aneurysms

Calcified deposits exist in almost all abdominal aortic aneurysms (AAAs). The significant difference in stiffness between these hard deposits and the compliant arterial wall may result in local stress concentrations and increase the risk of aneurysm rupture. Calcium deposits may also complicate AAA repair by hindering the attachment of a graft or stent-graft to the arterial wall or cause vessel wall injury at the site of balloon dilation or vascular clamp placement. Knowledge of the composition and properties of calcified deposits helps in understanding the risks associated with their presence. This work presents results of elemental composition, microscopic morphology, and mechanical property measurements of human calcified deposits obtained from within AAAs. The elemental analyses indicate the deposits are composed primarily of calcium phosphate with other assorted constituents. Microscopy investigations show a variety of microstructures within the deposits. The mechanical property measurements indicate an average elastic modulus in the range of cortical bone and an average hardness similar to nickel and iron.

Rapid disappearance of an endothelial ulceration in the left main coronary artery

A case is presented of a 65-year-old male who presented with an acute anterior wall myocardial infarction. An initial coronary angiogram demonstrated an ulcerated atherosclerotic plaque in the left main coronary artery. After 48 h of aggressive medical therapy including a 2b3a glycoprotein blocking agent, repeat angiography demonstrated resolution of the ulcerated plaque. The process of atherosclerotic plaque rupture is of dynamic nature.

Inflammation in atherosclerosis: visualizing matrix metalloproteinase action in macrophages in vivo

BACKGROUND

Matrix metalloproteinases (MMPs) in inflamed atherosclerotic plaques may contribute to extracellular matrix remodeling and the onset of acute thrombotic complications.

METHODS AND RESULTS

To test the hypothesis that optical molecular imaging with the use of an activatable near-infrared fluorescence (NIRF) probe can detect enzymatic action of MMP in atherosclerotic plaques, we used a NIRF substrate for gelatinases (MMP-2/gelatinase-A and MMP-9/gelatinase-B) in apolipoprotein E-deficient (apoE-/-) mice that consumed a high-cholesterol diet for 12 weeks and age-matched apoE+/+ mice as control. The aortas of apoE-/- mice at 24 hours after probe yielded intense NIRF signals, as detected by NIRF reflectance ex vivo, compared with negligible signals in aortas of apoE+/+ mice with/without probe administration or atherosclerotic apoE-/- aortas without probe. Gelatinase inhibitor treatment abolished NIRF signals in apoE-/- mouse aortas ex vivo. Sites of gelatinase activity visualized by NIRF colocalized with macrophage accumulation, immunoreactive MMP-2 and MMP-9, and gelatinolytic activity detected by in situ zymography. Furthermore, fluorescence molecular tomography indicated in vivo that atherosclerotic aortas of apoE-/- mice produced NIRF signals for gelatinase action, whereas aortas of apoE+/+ mice injected with the probe or apoE-/- aortas with no probe exhibited negligible NIRF signals.

CONCLUSIONS

These results suggest the feasibility of noninvasively imaging the enzymatic action of MMPs in vivo, an approach that may gauge inflammatory foci in atherosclerosis, assess cardiovascular risk, and evaluate the effects of therapeutic interventions.

How effective are rapid access chest pain clinics? Prognosis of incident angina and non-cardiac chest pain in 8762 consecutive patients

OBJECTIVE

To determine whether rapid access chest pain clinics are clinically effective by comparison of coronary event rates in patients diagnosed with angina with rates in patients diagnosed with non-cardiac chest pain and the general population.

DESIGN

Multicentre cohort study of consecutive patients with chest pain attending the rapid access chest pain clinics (RACPCs) of six hospitals in England.

PARTICIPANTS

8762 patients diagnosed with either non-cardiac chest pain (n = 6396) or incident angina without prior myocardial infarction (n = 2366) at first cardiological assessment, followed up for a median of 2.57 (interquartile range 1.96-4.15) years.

MAIN OUTCOME MEASURES

Primary end point--death due to coronary heart disease (International Classification of Diseases (ICD)10 I20-I25) or acute coronary syndrome (non-fatal myocardial infarction (ICD10 I21-I23), hospital admission with unstable angina (I24.0, I24.8, I24.9)). Secondary end points--all-cause mortality (ICD I20), cardiovascular death (ICD10 I00-I99), or non-fatal myocardial infarction or non-fatal stroke (I60-I69).

RESULTS

The cumulative probability of the primary end point in patients diagnosed with angina was 16.52% (95% confidence interval (CI) 14.88% to 18.32%) after 3 years compared with 2.73% (95% CI 2.29% to 3.25%) in patients with non-cardiac chest pain. Coronary standardised mortality ratios for men and women with angina aged <65 years were 3.52 (95% CI 1.98 to 5.07) and 4.39 (95% CI 1.14 to 7.64). Of the 599 patients who had the primary end point, 194 (32.4%) had been diagnosed with non-cardiac chest pain. These patients were younger, less likely to have typical symptoms, more likely to be south Asian and more likely to have a normal resting electrocardiogram than patients with angina who had the primary end point.

CONCLUSION

RACPCs are successful in identifying patients with incident angina who are at high coronary risk, but there is a need to reduce misdiagnosis and improve outcomes in patients diagnosed with non-cardiac chest pain who accounted for nearly one third of cardiac events during follow-up.

Long-term care after percutaneous coronary intervention: focus on the role of antiplatelet therapy

Arterial wall injury caused by percutaneous coronary intervention (PCI) triggers transient platelet activation and mural thrombosis; these effects are superimposed on the preexisting platelet hyperreactivity associated with underlying atherothrombosis. Platelet activation has been implicated in the major complications of PCI: acute and subacute thrombosis and restenosis. Antithrombotic and anticoagulant therapy minimizes thrombotic complications after PCI. Aspirin plus a thienopyridine (ticlopidine or clopidogrel) is more effective than aspirin plus heparin and extended warfarin therapy in preventing periprocedural ischemic events and subsequent stent thrombosis and results in less major and minor bleeding. Dual antiplatelet therapy with aspirin and clopidogrel (the preferred thienopyridine because of its superior hematologic safety) is recommended for at least 4 weeks to prevent subacute stent thrombosis with bare-metal stents and 3 to 6 months to prevent late-stent thrombosis with drug-eluting stents. Coronary atherothrombosis is a diffuse vascular disease, and reduction of the risk of future ischemic events requires strategies that extend beyond the focal treatment of stenotic lesions. Optimal long-term care after PCI requires aggressive systemic pharmacotherapy (antiplatelet agents, statins, beta-blockers, and angiotensin-converting enzyme Inhibitors) in conjunction with therapeutic lifestyle changes (smoking cessation, weight reduction, dietary measures, and exercise). In this context, dual antiplatelet therapy (aspirin plus clopidogrel) is recommended for at least 12 months after PCI for prophylaxis of future atherothrombotic events.

Intracoronary Thermography for Detection of High-Risk Vulnerable Plaques

Up to two-thirds of acute myocardial infarctions develop at sites of culprit lesions without a significant stenosis. New imaging techniques are needed to identify those lesions with an increased risk of developing an acute complication in the near future. Inflammation is a hallmark feature of these vulnerable/high-risk plaques. We have shown that inflamed atherosclerotic plaques are hot and their surface temperature correlates with an increased number of macrophages and decreased fibrous-cap thickness. Multiple animal and human experiments have shown that temperature heterogeneity correlates with arterial inflammation in vivo. Several coronary temperature mapping catheters are currently being developed and studied. These thermography methods can be used in the future to detect vulnerable plaques, potentially to determine patients' prognosis, and to study the plaque-stabilizing effects of different medications.

Atherosclerotic Plaque Characterization by Multidetector Row Computed Tomography Angiography

Multidetector row computed tomography angiography (MDCTA) is seen as a potential alternative to current imaging methods for the assessment of vessel anatomy and atherosclerotic plaque composition/morphology in a great variety of arterial beds. Recent advances represented by the increase in gantry speed to <500 ms per rotation and in the number of detector rows from 4 to 64, in addition to the decrease in slice thickness to submillimetric levels, brought significant improvement in diagnostic accuracy by coronary MDCTA. In general, it has a good correlation with both intravascular ultrasound (IVUS) and histopathology for discrimination between soft, intermediate, and calcified plaques. Plaque area and volume tend to be underestimated by 12-detector row MDCTA and overestimated by 16-detector row MDCTA, but the number of patients studied so far is relatively small. However, it seems that 64-detector row MDCTA can measure plaque area and volume with greater accuracy. Plaque remodeling is overestimated in small vessels by 12-detector row MDCTA, whereas 16- and 64-detector row MDCTA show a good correlation with IVUS. Although still under development, the potential of MDCTA to characterize atherosclerotic plaque composition as well as to precisely determine plaque area, volume, and remodeling in the future is quite promising.

Desensitization of platelet-derived growth factor receptor-beta by oxidized lipids in vascular cells and atherosclerotic lesions: prevention by aldehyde scavengers

The platelet-derived growth factor receptor-beta (PDGFRbeta) signaling pathway regulates smooth muscle cell (SMC) migration and proliferation and plays a role in the vascular wall response to injury. Oxidized low-density lipoprotein (oxLDL) in atherosclerotic lesions can activate the PDGFRbeta pathway, but the long-term effects of oxLDL on PDGFRbeta function are not well understood. We found that oxLDL induced a dual effect on PDGFRbeta signaling. Initial activation of the PDGFR was followed by desensitization of the receptor. PDGFRbeta desensitization was not attributable to PDGFRbeta degradation or changes in localization to the caveolae but instead resulted from decreased PDGF binding and inhibition of PDGFRbeta tyrosine kinase activity. This inhibition was associated with formation of (4HNE)- and acrolein-PDGFRbeta adducts and was mimicked by preincubation of cells with 4HNE. These PDGFRbeta adducts were also detected in aortae of apolipoprotein-deficient mice and hypercholesterolemic rabbits and in human carotid plaques. The aldehyde scavengers DNPH and Hydralazine prevented both oxLDL- and 4HNE-induced structural modification and PDGFRbeta signaling dysfunction in cells and in vivo. OxLDL inhibition of PDGF signaling may contribute to defective SMC proliferation and decrease the stability of a vulnerable plaque.

Abnormal soluble CD40 ligand and C-reactive protein concentrations in hypertension: relationship to indices of angiogenesis

BACKGROUND

Abnormal inflammation, platelets and angiogenesis are involved in the pathophysiology of cardiovascular disease (CVD).

OBJECTIVE

To test the hypothesis that concentrations of high sensitive C-reactive protein (CRP, an index of inflammation) and soluble CD40 ligand (sCD40L, an index of platelet activation) would be abnormal in hypertension, and in turn, be related to plasma indices of angiogenesis, the angiopoietins-1 and -2, and vascular endothelial growth factor (VEGF), in addition to the presence or absence of CVD.

METHODS

Using a cross-sectional approach, we measured plasma concentrations of CRP, sCD40L, VEGF, and angiopoietins-1 and -2 in 147 patients with hypertension (85 with a history of CVD event/s, 62 CVD event-free) and 68 age- and sex-matched healthy controls.

RESULTS

Concentrations of sCD40L (P = 0.039), CRP (P < 0.001), angiopoietin-1 (P < 0.001), angiopoietin-2 (P = 0.003) and VEGF (P < 0.001) were all greater amongst hypertensive patients than in controls. There were no significant differences in sCD40L and VEGF concentrations between hypertensive individuals with and without CVD events, but CRP and angiopoietin-1 concentrations were significantly greater amongst those with CVD events. On multiple regression analysis, sCD40L was associated with angiopoietin-2 (P = 0.01) and VEGF (P = 0.007) in hypertensive individuals, but no such associations were found within the healthy control group.

CONCLUSION

In patients with hypertension, sCD40L was associated with increased circulating markers of abnormal angiogenesis (angiopoietin-2, VEGF). The interaction between sCD40L and angiogenesis may contribute to the pathophysiology of CVD in hypertension.

Reflection spectroscopy of atherosclerotic plaque

Heart disease is the primary cause of death in the western world. Many of these deaths are caused by the rupture of vulnerable plaque. Vulnerable plaques are characterized by a large lipid core covered by a thin fibrous cap. One method for detecting these plaques is reflection spectroscopy. Several studies have investigated this method using statistical methods. A more analytic and quantitative study might yield more insight into the sensitivity of this detection modality. This is the approach taken in this work. Reflectance spectra in the spectral region from 400 to 1700 nm are collected from 77 measurement points from 23 human aortas. A measure of lipid content in a plaque based on reflection spectra is presented. The measure of lipid content is compared with the thickness of the lipid core, determined from histology. Defining vulnerable plaque as having a lipid core >500 microm and fibrous cap <500 microm, vulnerable plaques are detected with a sensitivity of 88% and a specificity of 94%. Although the method can detect lipid content, it is not very sensitive to the thickness of the fibrous cap. Another detection modality is necessary to detect this feature.

Intracoronary thermography: does it help us in clinical decision making?

The concept of the "vulnerable" plaque has recently emerged to explain how quiescent atherosclerotic lesions evolve to cause clinical events. The morphologic and immunologic determinants specific for the vulnerable plaque have been reported: a large lipid core (>or=40% plaque volume) composed of free cholesterol crystals, cholesterol esters, and oxidized lipids impregnated with tissue factor; a thin fibrous cap depleted of smooth muscle cells and collagen; an outward (positive) remodeling; inflammatory cell infiltration of fibrous cap and adventitia (mostly monocyte-macrophages, some activated T cells, and mast cells); and increased neovascularity. Despite the large amount of information regarding the morphological characteristics of remote lesions, we lack studies with functional assessment of non-culprit lesions. Coronary thermography is a technique for functional assessment of coronary atherosclerotic plaques. Several catheter designs have been proposed. There are catheters with thermistor(s) and wires with thermal sensors at the distal tip. All designs have several advantages and disadvantages. Despite the current limitations of coronary thermography, we gained important pathophysiological and clinical information regarding the vulnerability of atheromatic plaques. It has been documented both experimentally and clinically that increased heat generation is associated with increased macrophage concentration within the plaque. The correlation between local inflammatory involvement and local heat generation has also been observed with the peripheral inflammatory markers such as C-reactive protein. Whether systemic treatment, with agents such as statins or interventional techniques, such as drug-eluting stents, will have an impact on stabilizing vulnerable plaques need to be determined in future studies. In conclusion, although there are several techniques for evaluating morphologically atheromatic plaques, thermography is a promising method for the functional assessment of vulnerable plaque and has been introduced into clinical practice, with a good predictive value for clinical events in patients with increased temperature in the atherosclerotic plaque.

Positron autoradiography for intravascular imaging: feasibility evaluation

Approximately 70% of acute coronary artery disease is caused by unstable (vulnerable) plaques with an inflammation of the overlying cap and high lipid content. A rupturing of the inflamed cap of the plaque results in propagation of the thrombus into the lumen, blockage of the artery and acute ischaemic syndrome or sudden death. Morphological imaging such as angiography or intravascular ultrasound cannot determine inflammation status of the plaque. A radiotracer such as 18F-FDG is accumulated in vulnerable plaques due to higher metabolic activity of the inflamed cap and could be used to detect a vulnerable plaque. However, positron emission tomography (PET) cannot detect the FDG-labelled plaques because of respiratory and heart motions, small size and low activity of the plaques. Plaques can be detected using a miniature particle (positron) detector inserted into the artery. In this work, a new detector concept is investigated for intravascular imaging of the plaques. The detector consists of a storage phosphor tip bound to the end of an intravascular catheter. It can be inserted into an artery, absorb the 18F-FDG positrons from the plaques, withdrawn from the artery and read out. Length and diameter of the storage phosphor tip can be matched to the length and the diameter of the artery. Monte Carlo simulations and experimental evaluations of coronary plaque imaging with the proposed detector were performed. It was shown that the sensitivity of the storage phosphor detector to the positrons of 18F-FDG is sufficient to detect coronary plaques with 1 mm and 2 mm sizes and 590 Bq and 1180 Bq activities in the arteries with 2 mm and 3 mm diameters, respectively. An experimental study was performed using plastic tubes with 2 mm diameter filled with an FDG solution, which simulates blood. FDG spots simulating plaques were placed over the surface of the tube. A phosphor tip was inserted into the tube and imaged the plaques. Exposure time was 1 min in all simulations and experiments. Experiments showed that detecting the coronary plaques using the proposed technique is possible. The proposed technique has the potential for fast and accurate detection of vulnerable coronary and other intravascular plaques.

Lesional Overexpression of Matrix Metalloproteinase-9 Promotes Intraplaque Hemorrhage in Advanced Lesions But Not at Earlier Stages of Atherogenesis

Background— Matrix metalloproteinase-9 (MMP-9) is involved in atherosclerosis and elevated MMP-9 activity has been found in unstable plaques, suggesting a crucial role in plaque rupture. This study aims to assess the effect of MMP-9 on plaque stability in apolipoprotein E-deficient mice at different stages of plaque progression.

Methods and Results— Atherosclerotic lesions were elicited in carotid arteries by perivascular collar placement. MMP-9 overexpression in intermediate or advanced plaques was effected by intraluminal incubation with an adenovirus (Ad.MMP-9). A subset was coincubated with Ad.TIMP-1. Mock virus served as a control. Plaques were analyzed histologically. In intermediate lesions, MMP-9 overexpression induced outward remodeling, as shown by a 30% increase in media size ( p =0.03). In both intermediate and advanced lesions, prevalence of vulnerable plaque morphology tended to be increased. Half of MMP-9–treated lesions displayed intraplaque hemorrhage, whereas in controls and the Ad.MMP-9/Ad.TIMP-1 group this was 8% and 16%, respectively ( p =0.007). Colocalization with neovessels may point to neo-angiogenesis as a source for intraplaque hemorrhage.

Conclusion— These data show a differential effect of MMP-9 at various stages of plaque progression and suggest that lesion-targeted MMP-9 inhibition might be a valuable therapeutic modality in stabilizing advanced plaques, but not at earlier stages of lesion progression.

Rho-kinase inhibitor improves increased vascular resistance and impaired vasodilation of the forearm in patients with heart failure

BACKGROUND

Rho-kinase is suggested to have an important role in enhanced vasoconstriction in animal models of heart failure (HF). Patients with HF are characterized by increased vasoconstriction and reduced vasodilator responses to reactive hyperemia and exercise. The aim of the present study was to examine whether Rho-kinase is involved in the peripheral circulation abnormalities of HF in humans with the Rho-kinase inhibitor fasudil.

METHODS AND RESULTS

Studies were performed in patients with HF (HF group, n=26) and an age-matched control group (n=26). Forearm blood flow was measured with a strain-gauge plethysmograph during intra-arterial infusion of graded doses of fasudil or sodium nitroprusside. Resting forearm vascular resistance (FVR) was significantly higher in the HF group than in the control group. The increase in forearm blood flow evoked by fasudil was significantly greater in the HF group than in the control group. The increased FVR was decreased by fasudil in the HF group toward the level of the control group. By contrast, FVR evoked by sodium nitroprusside was comparable between the 2 groups. Fasudil significantly augmented the impaired ischemic vasodilation during reactive hyperemia after arterial occlusion of the forearm in the HF group but not in the control group. Fasudil did not augment the increased FVR evoked by phenylephrine in the control group significantly.

CONCLUSIONS

These results indicate that Rho-kinase is involved in increased FVR and impaired vasodilation of the forearm in patients with HF.

Distance from the ostium as an independent determinant of coronary plaque composition in vivo: an intravascular ultrasound study based radiofrequency data analysis in humans

AIMS

Relative plaque composition, more than its morphology alone, is thought to play a pivotal role in determining propensity to vulnerability. Thus, we investigated in vivo whether the distance from coronary ostium to plaque location independently affects plaque composition in humans. This may help explaining the recently reported non-uniform distribution of culprit lesions along the vessel in acute coronary syndromes.

METHODS AND RESULTS

In 51 consecutive patients (45 men), aged 38-76 years (mean age: 58+/-10), a non-culprit vessel was investigated through spectral analysis of IVUS radiofrequency data (IVUS-Virtual Histology). The study vessel was the left anterior descending artery in 23 (45%) patients; the circumflex artery in nine (18%), and right coronary artery in 19 (37%). The overall length of the region of interest, subsequently divided into 10 mm segments, was 41.5+/-13 mm long (range: 30.2-78.4). No significant change was observed in terms of relative plaque composition along the vessel with respect to fibrous, fibrolipidic, and calcified tissue, whereas the percentage of lipid core resulted to be increased in the first (median: 8.75%; IQR: 5.7-18) vs. the third (median: 6.1%; IQR: 3.2-12) (P=0.036) and fourth (median: 4.5%; IQR: 2.4-7.9) (P=0.006) segment. At multivariable regression analysis, distance from the ostium resulted to be an independent predictor of relative lipid content [beta=-0.28 (95%CI: -0.15, -0.41)], together with older age, unstable presentation, no use of statin, and presence of diabetes mellitus.

CONCLUSION

Plaque distance from the coronary ostium, as an independent determinant of relative lipid content, is potentially associated to plaque vulnerability in humans.

Identification of the ischemic etiology of heart failure by cardiovascular magnetic resonance imaging: diagnostic accuracy of late gadolinium enhancement

BACKGROUND

A large proportion of patients with heart failure (HF) have a large and poorly contracting left ventricle. The noninvasive recognition of the ischemic etiology of such patients is difficult, and for this purpose, usually patients undergo coronary angiography. It has been shown that cardiovascular magnetic resonance (CMR) imaging can detect myocardial scarring by evaluating late gadolinium enhancement (LGE). The diagnostic accuracy of such method in differentiating the etiology of HF has not been previously tested in an unselected HF ambulatory population.

METHODS

We studied 60 ambulatory patients consecutively enrolled from a specialized HF clinic. We included HF patients who were found to have increased left ventricular (LV) dimensions and reduced function. CMR was performed in these patients by operators who were unaware of patients' history and clinical conditions. LV dimensions and global and regional function, as well as the pattern of LGE, were obtained in each subject. Coronary angiography was subsequently performed in all the patients. The diagnostic accuracy of clinical history and electrocardiographic patterns, as well as regional wall motion abnormalities, wall thinning, and LGE, in differentiating coronary artery disease (CAD) from non-CAD patients were evaluated.

RESULTS

The majority of CAD patients (98%) showed LV contrast hyperenhancement with respect to non-CAD HF subjects (16%). The detection of LGE by CMR had a sensitivity of 98% and a specificity of 84% and an overall accuracy of 93% in detecting CAD etiology among HF patients.

CONCLUSIONS

LGE is able to accurately differentiate CAD from non-CAD etiology of HF and may represent a clinically useful noninvasive tool for this purpose. As it provides relevant functional information as well as insight into the etiology, CMR may be included among the most important diagnostic tools in the workup of patients with HF.

The renin-angiotensin system and atherosclerosis

Atherosclerosis is an insidious and complex disease of large- and medium-sized arteries. The primum movens of the disease is characterized by co-localization of lipids, inflammatory cells, and fibrous elements within the intima of vessels. Starting as a "fatty streak," the disease evolves over decades into complex lesions that can progress toward a stable or a vulnerable plaque. During the past decade, we have become familiar with the features of the vulnerable plaque; however, the mechanisms that cause a stable plaque to change into a vulnerable lesion with its dramatic clinical outcome still remain largely unknown. There is good evidence from epidemiologic, experimental, and clinical studies that the renin-angiotensin system, via its active peptide angiotensin II, may contribute to atherosclerosis development and progression, not only by increasing blood pressure but also through multiple direct effects. Moreover, recent studies have shown a potential role for angiotensin II as a mediator of plaque vulnerability.

Immunomodulation of atherosclerosis with a vaccine

Experimental observations have established that the innate and adaptive immune mechanisms both have roles in the modulation of atherosclerosis. The complex function that the immune system has in the pathophysiology of atherosclerosis is highlighted by the fact that both proatherogenic and atheroprotective effects of immune activation can be demonstrated. An immune response to the protein and lipid components of oxidized LDL cholesterol has been observed in experimental models, and immunization with these antigens has generally reduced atherosclerosis. The findings suggest the tantalizing possibility that an atheroprotective vaccine can be developed. Our laboratories have identified several antigenic epitopes in the human apolipoprotein B100 component of LDL cholesterol. Active immunization with some of these epitopes has reduced atherosclerosis in hyperlipidemic mice. We believe, therefore, that a vaccine based on apolipoprotein B100-related peptide could have a role in reducing atherosclerosis. In this review, we discuss the possible immunologic mechanisms by which vaccines against atherosclerosis might work and the ways in which such treatment might be most effectively administered.

C-reactive protein increases matrix metalloproteinase-2 expression and activity in cultured human vascular smooth muscle cells

The C-reactive protein (CRP) is a strong predictor of cardiovascular events both in the general population and in patients with coronary artery disease. We aimed to evaluate whether in cultured human vascular smooth muscle cells (hVSMC) CRP modulates the synthesis and release of metalloproteinase-2 (MMP-2), which is deeply involved in plaque instabilization and vascular remodeling, and of the tissue inhibitor of metalloproteinase-2 (TIMP-2). Both in supernatants and in cell lysates of cultured hVSMC exposed to CRP (0-10 mg/L), we evaluated MMP-2 activity (gelatin zymography), MMP-2 and TIMP-2 protein synthesis (immunoblotting), MMP-2 and TIMP-2 mRNA expression (reverse transcription-polymerase chain reaction). CRP effects were also investigated after cell exposure to specific MEK inhibitor PD98059 (15-30 micromol/L) to evaluate the involvement of mitogen-activated protein kinase (MAPK). CRP upregulated MMP-2 mRNA expression. MMP-2 synthesis and activity were increased by 1-10 mg/L CRP starting from 8-hour incubation. The effect was prevented by exposure to PD98059. CRP did not modify TIMP-2 mRNA expression, protein synthesis, and secretion. CRP, at concentrations that predict cardiovascular events, upregulates MMP-2 mRNA expression and increases MMP-2 protein synthesis and release in hVSMC through mechanisms involving activation of MAPK pathway. These data indicate that CRP is not only a risk marker for vascular events, but it is also directly involved in the mechanisms leading to remodeling and instabilization of atherosclerotic plaque.

Initial Appraisal of Acute Coronary Syndromes

Acute coronary syndrome remains a daunting health care problem in the United States. One third of emergency department patients with chest pain will eventually have a diagnosis of acute coronary syndrome. During the past decade, there have been many advances in the treatment of acute coronary syndrome as well as a widespread movement in emergency medicine to streamline the process of its treatment. Goals of emergency department care include rapid identification of patients with acute myocardial infarction, exclusion of causes of nonischemic chest pain, stratification of patients with acute coronary ischemia into low-risk and high-risk groups, and initiation of pharmacologic treatments. These goals will be discussed in this review, with particular emphasis on pharmacologic treatments.

Longitudinal Structural Determinants of Atherosclerotic Plaque Vulnerability

OBJECTIVES

This study theoretically examined the longitudinal structural determinants of plaque vulnerability using a color-coded stress mapping technique for several hypothetical vessel models as well as three-dimensional intravascular ultrasound (IVUS) images with use of a finite element analysis.

BACKGROUND

It has been shown that an excessive concentration of stress is related to atherosclerotic plaque rupture. However, the local determinants of in-plaque longitudinal stress distribution along the coronary arterial wall remain unclear.

METHODS

Using a finite element analysis, we performed a color mapping of equivalent stress distribution within plaques for three-dimensional vessel models as well as longitudinal IVUS plaque images (n = 15). Then, the effects of plaque size, shape, expansive remodeling, calcification, and lipid core on the equivalent stress distribution were examined.

RESULTS

The color mapping of vessel models revealed a concentration of equivalent stress at the top of the hills and the shoulders of homogeneous fibrous plaques. Expansive remodeling and the lipid core augmented the surface equivalent stress, whereas luminal stenosis and superficial calcification attenuated the equivalent stress. The location of excessive stress concentration was modified by the distribution of the lipid core and calcification. The thickness of the fibrous cap was inversely related to the equivalent stress within the fibrous cap. However, the color mapping of IVUS plaque images showed that the equivalent stress value at the fibrous cap varied with changes in plaque shape and superficial calcification, even when the thickness of the fibrous cap remained constant.

CONCLUSIONS

A distribution analysis of longitudinal stress revealed specific effects of plaque shape, size, and remodeling, as well as effects of the interior distribution of tissue components, on the concentration of stress at the plaque surface. Moreover, fibrous caps of the same thickness did not consistently represent the same vulnerability to rupture.

Novel determinants of plaque instability

Arachidonic acid metabolism plays an important role in acute ischemic syndromes affecting the coronary or cerebrovascular territory, as reflected by biochemical measurements of eicosanoid biosynthesis and the results of inhibitor trials in these settings. Two cyclooxygenase (COX)-isozymes have been characterized, COX-1 and COX-2, that differ in terms of regulatory mechanisms of expression, tissue distribution, substrate specificity, preferential coupling to upstream and downstream enzymes and susceptibility to inhibition by the extremely heterogeneous class of COX-inhibitors. While the role of platelet COX-1 in acute coronary syndromes and ischemic stroke is firmly established through approximately 20 years of thromboxane metabolite measurements and aspirin trials, the role of COX-2 expression and inhibition in atherothrombosis is substantially uncertain, because the enzyme was first characterized in 1991 and selective COX-2 inhibitors became commercially available only in 1998. In this review, we discuss the pattern of expression of COX-2 in the cellular players of atherothrombosis, its role as a determinant of plaque 'vulnerability,' and the clinical consequences of COX-2 inhibition. Recent studies from our group suggest that variable expression of upstream and downstream enzymes in the prostanoid biosynthetic cascade may represent important determinants of the functional consequences of COX-2 expression and inhibition in different clinical settings.

Cytokines and growth factors involved in apoptosis and proliferation of vascular smooth muscle cells

This review focuses on the role of cytokines and growth factors involved in the regulation of smooth muscle cells in an atherosclerotic plaque. As a plaque begins to develop, upon endothelial injury inflammatory cells within the lesion interact with the accumulating LDL, other inflammatory cells and smooth muscle cells and release cytokines and growth factors. The mediators released from the activated cells regulate the proliferation and/or survival of smooth muscle cells. This determines the stability and integrity of a plaque. New data emerging from various studies have provided novel insights into many of the cellular interactions and signaling mechanisms involving apoptosis of smooth muscle cells in the atherosclerotic plaques. A number of these studies, focusing on activation of inflammatory cells and the roles of chemokines, cytokines and growth factors, are addressed in this review.

Protective Effects of Angiotensin II Interruption: Evidence for Antiinflammatory Actions

Angiotensin II, the major effector molecule produced from the renin-angiotensin-aldosterone axis, is a vasoconstrictor contributing to hypertension. Evidence indicates, however, that angiotensin II also is a potent proinflammatory mediator with growth and remodeling effects. In vitro and in vivo studies have shown that angiotensin II blockade significantly reduces concentrations of proinflammatory mediators and oxidative stress products in numerous inflammatory models. Interruption of angiotensin II activity with angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers has been beneficial for patients with inflammatory diseases. Much of this benefit occurs independent of the antihypertensive effect of angiotensin II interruption, suggesting a distinctive protective mechanism. Angiotensin II receptor blockers may represent a novel class of antiinflammatory drugs with indications far beyond cardiovascular diseases.

National data elements for the clinical management of acute coronary syndromes

Patients with acute coronary syndromes represent a clinically diverse group and their care remains heterogeneous. These patients account for a significant burden of morbidity and mortality in Australia. Optimal patient outcomes depend on rapid diagnosis, accurate risk stratification and the effective implementation of proven therapies, as advocated by clinical guidelines. The challenge is in effectively applying evidence in clinical practice. Objectivity and standardised quantification of clinical practice are essential in understanding the evidence-practice gap. Observational registries are key to understanding the link between evidence-based medicine, clinical practice and patient outcome. Data elements for monitoring clinical management of patients with acute coronary syndromes have been adapted from internationally accepted definitions and incorporated into the National Health Data Dictionary, the national standard for health data definitions in Australia. Widespread use of these data elements will assist in the local development of "quality-of-care" initiatives and performance indicators, facilitate collaboration in cardiovascular outcomes research, and aid in the development of electronic data collection methods.

Diagnosis of thin-cap fibroatheromas by a self-contained intravascular magnetic resonance imaging probe in ex vivo human aortas and in situ coronary arteries

OBJECTIVES

We sought to correlate findings obtained from a self-contained magnetic resonance imaging (MRI) probe with plaque morphology of ex vivo human aortas and coronary arteries.

BACKGROUND

Early detection of thin-cap fibroatheromas (TCFAs) may allow for early preventive treatment of acute coronary syndromes. We developed an intravascular MRI catheter capable of imaging the arterial wall without external magnets or coils by differentiating lipid-rich and fibrotic-rich areas of the atherosclerotic plaque on the basis of differential water diffusion.

METHODS

Aortic samples (n = 16) and coronary arteries were obtained within 12 h of death. Coronary specimens were intermediate in angiographic severity (30% to 60% luminal narrowing, n = 18). Blinded histologic and immunohistochemical analyses of the tissues were performed and correlated to MRI findings.

RESULTS

The 16 aortic lesions included four ulcerated plaques, two TCFAs, two thick-cap fibrous atheromas, two intimal xanthomas, and six adaptive intimal thickenings. The MRI scan correctly correlated with the histologic diagnosis in 15 (94%) of 16 lesions. The 18 coronary lesions included one plaque rupture, three TFCAs, seven thick-cap fibrous atheromas, four fibrocalcific plaques, two intimal xanthomas, and one adaptive intimal thickening. The MRI scan correlated with the histologic diagnosis in 16 of 18 lesions (sensitivity 100%, specificity 89%).

CONCLUSIONS

The self-contained intravascular MRI catheter successfully identified TCFA and may prove to be an important diagnostic approach to determining the presence of lesions with increased risk of causing death or myocardial infarction.

Enhanced T-helper-1 lymphocyte activation patterns in acute coronary syndromes

OBJECTIVES

We sought to determine whether different stages of coronary artery disease (CAD) are associated with distinct differentiation patterns of activated T cells.

BACKGROUND

Atherosclerosis is an inflammatory disease. However, little is known about specific inflammatory cell activation in atherosclerosis, for example, the T-helper (Th)1/Th2-balance.

METHODS

We studied 18 patients with stable angina (SA), 28 patients with acute coronary syndrome (ACS) (16 with unstable angina pectoris and 12 with ST-segment elevation myocardial infarction), 19 patients with unheralded myocardial infarction (UH), and 16 control patients. Cytokine patterns and transcription factor signaling pathways of circulating T cells were characterized using reverse transcription polymerase chain reaction and flow cytometry.

RESULTS

Although interferon (IFN)-gamma(+)/CD3(+) T cells were approximately 2-fold greater in patients with SA or UH than in control subjects, there was a massive expansion of Th1 cells in patients with ACS (p < 0.001). This increase was paralleled by significantly increased mRNA transcript levels for signal-transducer-and-activator-4 (ACS 1.17 +/- 0.14 relative units [RU]; control patients 0.44 +/- 0.09 RU; SA 0.67 +/- 0.12 RU; UH 0.61 +/- 0.17 RU), interleukin-2 (ACS 1.55 +/- 0.51 RU; control patients 0.21 +/- 0.09 RU; SA 0.54 +/- 0.18 RU; UH 0.45 +/- 0.16 RU), and IFN-gamma in ACS (1.27 +/- 0.39 RU; control patients 0.35 +/- 0.09 RU; SA 0.58 +/- 0.11 RU; UH 0.53 +/- 0.24 RU; p < 0.002). Th2 and Th0 cells were not different across patient subsets. The burden of CAD was identical between SA (1.4 +/- 0.2 diseased vessels, 68 +/- 13% diameter stenosis) and ACS (1.4 +/- 0.2 diseased vessels, 64 +/- 17% diameter stenosis) but significantly greater in patients with UH (2.5 +/- 0.5 diseased vessels, 95 +/- 7% diameter stenosis; p < 0.05).

CONCLUSIONS

Patients with UH have a greater burden of obstructive CAD than SA but no greater T-cell activation. Patients with ACS have the same extent of CAD than SA but significantly greater activation of Th1 cells that may contribute to the increasing instability. Differences in circulating Th1 cells might indicate different pathogenic components, leading to ACS and UH.

Rho-kinase is an important therapeutic target in cardiovascular medicine

Rho-kinase has been identified as one of the effectors of the small GTP-binding protein Rho. Accumulating evidence has demonstrated that Rho/Rho-kinase pathway plays an important role in various cellular functions, not only in vascular smooth muscle cell (VSMC) contraction but also in actin cytoskeleton organization, cell adhesion and motility, cytokinesis, and gene expressions, all of which may be involved in the pathogenesis of cardiovascular disease. At molecular level, Rho-kinase upregulates various molecules that accelerate inflammation/oxidative stress, thrombus formation, and fibrosis, whereas it downregulates endothelial nitric oxide synthase. The expression of Rho-kinase itself is mediated by protein kinase C/NF-kappaB pathway with an inhibitory and stimulatory modulation by estrogen and nicotine, respectively. At cellular level, Rho-kinase mediates VSMC hypercontraction, stimulates VSMC proliferation and migration, and enhances inflammatory cell motility. In animal studies, Rho-kinase has been shown to be substantially involved in the pathogenesis of vasospasm, arteriosclerosis, ischemia/reperfusion injury, hypertension, pulmonary hypertension, stroke and heart failure, and to enhance central sympathetic nerve activity. Finally, in clinical studies, fasudil, a Rho-kinase inhibitor, is effective for the treatment of a wide range of cardiovascular disease, including cerebral and coronary vasospasm, angina, hypertension, pulmonary hypertension, and heart failure, with a reasonable safety. Thus, Rho-kinase is an important therapeutic target in cardiovascular medicine.

Matrix metalloproteinases and diabetic vascular complications

Diabetes mellitus (DM) is associated with an increased incidence of cardiovascular events and microvascular complications. These complications contribute to the morbidity and mortality associated with DM. There is increasing evidence supporting a role for matrix metalloproteinases (MMPs) and their inhibitors (tissue inhibitors of matrix metalloproteinases - TIMPs) in the atherosclerotic process. However, the relationship between MMPs/TIMPs and diabetic angiopathy is less well defined. Hyperglycemia directly or indirectly (eg, via oxidative stress or advanced glycation products) increases MMP expression and activity. These changes are associated with histologic alterations in large vessels. On the other hand, low proteolytic activity of MMPs contributes to diabetic nephropathy. Within atherosclerotic plaques an imbalance between MMPs and TIMPs may induce matrix degradation, resulting in an increased risk of plaque rupture. Furthermore, because MMPs enhance blood coagulability, MMPs and TIMPs may play a role in acute thrombotic occlusion of vessels and consequent cardiovascular events. Some drugs can inhibit MMP activity. However, the precise mechanisms involved are still not defined. Further research is required to demonstrate the causative relationship between MMPs/TIMPs and diabetic atherosclerosis. It also remains to be established if the long-term administration of MMP inhibitors can prevent acute cardiovascular events.

Vessel wall apoptosis and atherosclerotic plaque instability

Atherosclerotic cardiovascular disease remains the leading cause of death in the industrialized world. Most cardiovascular deaths result from acute coronary syndromes, including unstable angina pectoris and acute myocardial infarction. Coronary syndromes often arise from acute coronary thrombosis, itself commonly a result of disruption or rupture of the fibrous cap of a lipid-laden atherosclerotic plaque. Despite this huge clinical burden of atherosclerotic plaque instability, our understanding of the molecular mechanisms mediating atherosclerotic plaque disruption and rupture, at a cellular level, remains limited. Placed in a clinical context, this review discusses our current understanding of the molecular basis for atherosclerotic plaque instability, with particular emphasis on the process of apoptosis-or programmed cell death-seen increasingly as playing a key role in a number of cell types within the vessel wall.

Angiopoietin-1 and angiopoietin-2 in diabetes mellitus: relationship to VEGF, glycaemic control, endothelial damage/dysfunction and atherosclerosis

BACKGROUND

microvascular complications in diabetes identify those at risk of cardiovascular disease (CVD), suggesting a link between abnormal neovascularisation and CVD. This may be related to high plasma vascular endothelial growth factor (VEGF). We hypothesised increased angiopoietins (Ang)-1 and -2 in patients with diabetes that are related to VEGF, medium-term glycaemic control, endothelial damage/dysfunction and atherosclerosis.

METHODS AND PATIENTS

we measured plasma Ang-1 and Ang-2 alongside VEGF (all by ELISA) in 96 patients with type-2 diabetes mellitus (41 with and 56 without overt CVD) who were compared to 35 age- and sex-comparable healthy controls. Common carotid intima-media thickness (CC-IMT) was used to assess carotid atherosclerosis, plasma von Willebrand factor (vWf) and urine albumin:creatinine ratio (UACr) to quantify and endothelial damage/dysfunction, and HbA1c to mark medium-term hypergylcaemia.

RESULTS

Ang-2 (but not Ang-1) was higher in patients with diabetes compared to controls (p<0.01), with no significant difference between patients with and without CVD. As expected, CC-IMT, UACr, HbA1c, vWf, and VEGF were also abnormal in the patients. Within the patient group alone, and in the entire cohort, VEGF and Ang-2 correlated strongly (both p<0.001) and with several other markers. However, in multivariate analysis, the only significant relationship that remained after adjustments was between VEGF and HbA1c (p<0.001).

CONCLUSIONS

Angiogenic growth factor Ang-2, like VEGF, is raised in diabetes regardless of vascular disease. Both growth factors correlated with HbA1c and with each other, not with endothelial injury or atherosclerosis, but after multiple adjustment, only that between HbA1c and VEGF significant remained. VEGF is likely to have a more prominent role in diabetes than Ang-2.

TLR signaling: an emerging bridge from innate immunity to atherogenesis

Chronic inflammation and disordered lipid metabolism represent hallmarks of atherosclerosis. Considerable evidence suggests that innate immune defense mechanisms might interact with proinflammatory pathways and contribute to development of arterial plaques. The preponderance of such evidence has been indirect clinical and epidemiologic studies, with some support from experimental animal models of atherosclerosis. However, recent data now directly implicate signaling by TLR4 in the pathogenesis of atherosclerosis, establishing a key link between atherosclerosis and defense against both foreign pathogens and endogenously generated inflammatory ligands. In this study, we briefly review these and closely related studies, highlighting areas that should provide fertile ground for future studies aimed at a more comprehensive understanding of the interplay between innate immune defense mechanisms, atherosclerosis, and related vascular disorders.

Molecular imaging of atherosclerotic plaques using a human antibody against the extra-domain B of fibronectin

Current imaging modalities of human atherosclerosis, such as angiography, ultrasound, and computed tomography, visualize plaque morphology. However, methods that provide insight into plaque biology using molecular tools are still insufficient. The extra-domain B (ED-B) is inserted into the fibronectin molecule by alternative splicing during angiogenesis and tissue remodeling but is virtually undetectable in normal adult tissues. Angiogenesis and tissue repair are also hallmarks of advanced plaques. For imaging atherosclerotic plaques, the human antibody L19 (specific against ED-B) and a negative control antibody were labeled with radioiodine or infrared fluorophores and injected intravenously into atherosclerotic apolipoprotein E-null (ApoE-/-) or normal wild-type mice. Aortas isolated 4 hours, 24 hours, and 3 days after injection exhibited a selective and stable uptake of L19 when using radiographic or fluorescent imaging. L19 binding was confined to the plaques as assessed by fat staining. Comparisons between fat staining and autoradiographies 24 hours after 125I-labeled L19 revealed a significant correlation (r=0.89; P<0.0001). Minimal antibody uptake was observed in normal vessels from wild-type mice receiving the L19 antibody and in atherosclerotic vessels from ApoE-/- mice receiving the negative control antibody. Immunohistochemical studies revealed increased expression of ED-B not only in murine but also in human plaques, in which it was found predominantly around vasa vasorum and plaque matrix. In summary, we demonstrate selective targeting of atheromas in mice using the human antibody to the ED-B domain of fibronectin. Thus, our findings may set the stage for antibody-based molecular imaging of atherosclerotic plaques in the intact organism.