LeRoy E. Rabbani

Adverse vascular effects of homocysteine are modulated by endothelium-derived relaxing factor and related oxides of nitrogen.

Elevated levels of homocysteine are associated with an increased risk of atherosclerosis and thrombosis. The reactivity of the sulfhydryl group of homocysteine has been implicated in molecular mechanisms underlying this increased risk. There is also increasingly compelling evidence that thiols react in the presence of nitric oxide (NO) and endothelium-derived relaxing factor (EDRF) to form S-nitrosothiols, compounds with potent vasodilatory and antiplatelet effects. We, therefore, hypothesized that S-nitrosation of homocysteine would confer these beneficial bioactivities to the thiol, and at the same time attenuate its pathogenicity. We found that prolonged (> 3 h) exposure of endothelial cells to homocysteine results in impaired EDRF responses. By contrast, brief (15 min) exposure of endothelial cells, stimulated to secrete EDRF, to homocysteine results in the formation of S-NO-homocysteine, a potent antiplatelet agent and vasodilator. In contrast to homocysteine, S-NO-homocysteine does not support H2O2 generation and does not undergo conversion to homocysteine thiolactone, reaction products believed to contribute to endothelial toxicity. These results suggest that the normal endothelium modulates the potential, adverse effects of homocysteine by releasing EDRF and forming the adduct S-NO-homocysteine. The adverse vascular properties of homocysteine may result from an inability to sustain S-NO formation owing to a progressive imbalance between the production of NO by progressively dysfunctional endothelial cells and the levels of homocysteine.

Role of Clopidogrel Loading Dose in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Angioplasty: Results From the HORIZONS-AMI (Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction) Trial

OBJECTIVES Our aim was to determine whether a 600-mg loading dose of clopidogrel compared with 300 mg results in improved clinical outcomes in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). BACKGROUND A 600-mg loading dose of clopidogrel compared with 300 mg provides more rapid and potent inhibition of platelet activation. METHODS In the HORIZONS-AMI (Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction) trial, 3,602 patients with STEMI undergoing primary PCI were randomized to bivalirudin (n = 1,800) or unfractionated heparin plus a glycoprotein IIb/IIIa inhibitor (n = 1,802). Randomization was stratified by thienopyridine loading dose, which was determined before random assignment. RESULTS Patients in the 600-mg (n = 2,158) compared with the 300-mg (n = 1,153) clopidogrel loading dose group had significantly lower 30-day unadjusted rates of mortality (1.9% vs. 3.1%, p = 0.03), reinfarction (1.3% vs. 2.3%, p = 0.02), and definite or probable stent thrombosis (1.7% vs. 2.8%, p = 0.04), without higher bleeding rates. Compared with unfractionated heparin plus a glycoprotein IIb/IIIa inhibitor, bivalirudin monotherapy resulted in similar reductions in net adverse cardiac event rates within the 300-mg (15.2% vs. 12.3%) and 600-mg (10.4% vs. 7.3%) clopidogrel loading dose subgroups (p(interaction) = 0.41). By multivariable analysis, a 600-mg clopidogrel loading dose was an independent predictor of lower rates of 30-day major adverse cardiac events (hazard ratio: 0.72 [95% confidence interval: 0.53 to 0.98], p = 0.04). CONCLUSIONS In patients with STEMI undergoing primary PCI with contemporary anticoagulation regimens, a 600-mg loading dose of clopidogrel may safely reduce 30-day ischemic adverse event rates compared with a 300-mg loading dose. (Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction [HORIZONS-AMI]; NCT00433966).

Role for p27(Kip1) in Vascular Smooth Muscle Cell Migration.

BACKGROUND Rapamycin is a potent inhibitor of smooth muscle cell (SMC) proliferation and migration. Rapamycin-mediated inhibition of SMC proliferation is associated with upregulation of the cyclin-dependent kinase inhibitor p27(Kip1). Previously, we showed that mixed embryonic fibroblasts obtained from p27(Kip1)(-/-) mice were relatively rapamycin-resistant, suggesting that p27(Kip1) plays an integral role in modulating the antiproliferative effects of rapamycin. We hypothesized that the antimigratory effect of rapamycin may also be mediated by p27(Kip1). METHODS AND RESULTS Rapamycin (1 to 10 nmol/L) inhibited basic fibroblast growth factor-induced migration of wild-type (WT) but not p27(Kip1)(-/-) SMCs in a dose-dependent manner (P<0.05) in a modified Boyden chamber. The effects of rapamycin on aortic SMC explant migration were also studied with WT, p27(+/-), and p27(-/-) mice. Rapamycin 4 mg. kg(-1). d(-1) IP for 5 days inhibited SMC migration by 90% in the WT and p27(Kip1)(+/-) (P<0.05) but not p27(Kip1)(-/-) animals. CONCLUSIONS Lack of p27(Kip1) reduces rapamycin-mediated inhibition of SMC migration. These novel findings suggest a role for p27(Kip1) in the signaling pathway(s) that regulates SMC migration.

Elevated Levels of Plasma C-Reactive Protein Are Associated With Decreased Graft Survival in Cardiac Transplant Recipients

BackgroundInflammation may be involved in the origin of transplant coronary artery disease. We hypothesized that plasma levels of C-reactive protein (CRP) and interleukin-6 (IL-6), markers for systemic inflammation, would correlate with cardiac transplant graft survival. Methods and ResultsWe studied 99 consecutive cardiac transplant recipients who were referred for routine endomyocardial biopsy and/or surveillance coronary angiography. Plasma levels of CRP and IL-6 were measured by their respective ELISAs. Patients were divided into 2 groups: those who died or required retransplantation and those who survived without the need for retransplantation. During the follow-up period of 5.0±2.7 years (range, 0.2 to 15.1 years) after transplant, 20 patients died and 9 required retransplantation. There was no significant difference in age, race, sex, cause of native myopathy, presence of diabetes, or use of aspirin, statins, or calcium channel blockers between the 2 groups. Although IL-6 did not relate to graft failure, CRP level was predictive of allograft failure (P =0.003). The risk of allograft failure increased 36% for every 2-fold increase in CRP level. Moreover, CRP levels also correlated significantly with the frequency of grade 3 rejection (P =0.02). In multivariate analysis, when combined with other significant predictors such as donor age and sex mismatching of the graft, CRP still significantly predicted graft failure (P =0.025) with a 32% increase in the risk of graft failure for every 2-fold increase in CRP level. ConclusionsThese findings suggest that elevated plasma levels of CRP are associated with subsequent allograft failure in cardiac transplant recipients.

Inflammatory Biomarkers of Vascular Risk as Correlates of Leukoariosis

Background and Purpose— Inflammatory biomarkers, including lipoprotein-associated phospholipase A2 (Lp-PLA2), myeloperoxidase (MPO), and high-sensitivity C-reactive protein (hsCRP) are associated with ischemic stroke risk. White matter hyperintensities (WMH) seen on brain MRI scans are associated with vascular risk factors and an increased risk of incident stroke, but their relation to inflammatory biomarkers is unclear. Methods— The Northern Manhattan Study includes a stroke-free community-based sample of Hispanic, black, and white participants with quantitative measurement of WMH volume (WMHV) and inflammatory biomarkers. We measured the association between Lp-PLA2, MPO, and hsCRP levels, and log-transformed WMHV after adjusting for sociodemographic and vascular risk factors. Results— The hsCRP (median, 2.42 mg/L; IQR, 1.04, 5.19), Lp-PLA2 (median, 220.97 ng/mL; IQR, 185.77, 268.05), and MPO (median, 15.14 ng/mL; IQR, 12.32, 19.69) levels were available in 527 The Northern Manhattan Study participants with WMHV data but no subclinical infarcts. Those with hsCRP in the upper quartile (Q4 >4.92 mg/L or >3 mg/L), Lp-PLA2 in Q4 (≥264.9 ng/mL), or MPO levels in Q3 (15.04–19.39 ng/mL) or Q4 (>19.39 ng/mL) each had greater WMHV, adjusting for sociodemographic and vascular risk factors. Adjusting for all biomarkers simultaneously, WMHV was 1.3-fold greater for Lp-PLA2 levels in Q4 compared to Q1 (&bgr;=0.28; P =0.008) and 1.25-fold greater for MPO levels above the median compared to below (&bgr;=0.22; P =0.02), but hsCRP was not associated with WMHV. Conclusions— Relative elevations of the inflammatory markers Lp-PLA2 and MPO were associated with a greater burden of WMH independent of hsCRP.

Intravascular ultrasound assessment of the incidence and predictors of edge dissections after drug-eluting stent implantation.

OBJECTIVES We used intravascular ultrasound (IVUS) to assess incidence, predictors, morphology, and angiographic findings of edge dissections after drug-eluting stent (DES) implantation. BACKGROUND DES implantation strategies differ compared with bare-metal stenting; coronary dissections after DES implantation have not been well studied. METHODS We studied 887 patients with 1,045 non-in-stent restenosis lesions in 977 native arteries undergoing DES implantation with IVUS imaging. RESULTS Eighty-two dissections were detected; 51.2% (42 of 82) involved the proximal and 48.8% (40 of 82) the distal stent edge. Residual plaque area (8.0 +/- 4.3 mm(2) vs. 5.2 +/- 3.0 mm(2), p < 0.0001); plaque burden (52.2 +/- 11.7% vs. 36.2 +/- 15.3%, p < 0.0001); plaque eccentricity (8.4 +/- 5.5 vs. 4.0 +/- 3.4, p < 0.0001); and stent edge symmetry (1.2 +/- 0.1 vs. 1.1 +/- 0.1, p = 0.02) were larger; plaque burden > or =50% was more frequent (62.0% vs. 17.2%, p < 0.0001); calcium deposits (52.1% vs. 35.2%, p = 0.03) more common; and lumen-to-stent-edge-area ratio (0.9 +/- 0.2 vs. 1.0 +/- 0.2, p < 0.0001) was smaller in the edge dissection group compared with the nondissection group. Intramural hematomas occurred in 34.1% (28 of 82) of dissections. When compared with nonhematoma dissections, residual plaque and media area (6.4 +/- 2.5 mm(2) vs. 8.9 +/- 4.6 mm(2), p = 0.04) was smaller, and stent edges less asymmetric (1.1 +/- 0.1 vs. 1.2 +/- 0.1, p = 0.009) in the dissection with hematoma group. Independent predictors of any stent edge dissection were residual plaque eccentricity (odds ratio [OR]: 1.4, p = 0.02), lumen-to-stent-edge-area ratio (OR: 0.0, p = 0.007), and stent edge symmetry (OR: 1.2, p = 0.02 for each 0.01 increase). CONCLUSIONS IVUS identified edge dissections after 9.2% of DES implantations. Residual plaque eccentricity, lumen-to-stent-edge-area ratio, and stent edge symmetry predicted coronary stent edge dissections. Dissections in less diseased reference segments more often evolved into an intramural hematoma.

Recent observations on the role of hemostatic determinants in the development of the atherothrombotic plaque

Recent evidence suggests that hemostatic determinants play a major role in the evolution of the atherothrombotic plaque. Platelets can serve as cholesterol donors for macrophages, thereby facilitating foam cell formation. Lipoprotein(a) inhibits fibrinolysis and may also contribute to atherogenesis by serving as a ligand for the scavenger receptor. By complexing with fibrin(ogen) in atheromatous lesions, lipoprotein(a) attenuates clearance of this protein, promoting atherogenesis and vascular dysfunction. These observations suggest that thrombotic determinants are critical for the development of the atheromatous plaque, and may guide the appropriate selection of potential therapeutic options in the future.

Circulating Levels of IL-1β, a Prothrombotic Cytokine, are Elevated in Unstable Angina Versus Stable Angina

Background: Multiple studies support a role for inflammation in the pathogenesis of coronary atherosclerosis and unstable cardiac syndromes. However, of the known proinflammatory cytokines, only elevated plasma levels of interleukin-6 have been linked to unstable angina. We sought to examine the plasma levels of other major proinflammatory cytokines in similar clinical settings and to determine the extent of the relationship between inflammation and unstable coronary syndromes by measuring the levels of various proinflammatory cytokines in patients with stable and unstable angina.Methods: We measured plasma levels of interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), and interleukin 6 (IL-6) in 97 patients: 67 with stable angina, 24 with unstable angina, and 15 healthy controls.Results: Mean levels of IL-1β were significantly higher in patients with unstable angina as compared to patients with stable angina (p = .009). Levels of IL-6 were significantly higher than control patients for both stable angina and unstable angina patients (p = .031 and .006, respectively). No significant differences were found in the levels of TNF-α.Conclusions: Our results suggest that both IL-1β and IL-6 contribute to the pathogenesis of unstable angina, and that the profile of circulating plasma levels of proinflammatory cytokines differs in unstable angina from that in stable angina.Abbreviated Abstract. Multiple studies support a role for inflammation in the pathogenesis of coronary atherosclerosis and unstable cardiac syndromes. We measured plasma levels of interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), and interleukin 6 (IL-6) in patients with stable and unstable coronary syndromes. Levels of IL-1β and IL-6 were found to be elevated in patients with unstable coronary syndromes. No significant differences were found in the levels of TNF-α. Our results suggest that both IL-1β and IL-6 contribute to the pathogenesis of unstable angina.

Time course of improvement in ventricular function after ablation of incessant automatic atrial tachycardia

A patient with dilated cardiomyopathy and supraventricular tachycardia presumed to be of sinus origin was referred for cardiac transplantation. The extreme rate of the tachycardia during exercise, profound fluctuations in heart rate, and the presence of an abnormal P wave axis suggested the diagnosis of incessant ectopic atrial tachycardia rather than compensatory sinus tachycardia. Electrophysiologic study with endocardial activation sequence mapping confirmed the diagnosis of an ectopic left atrial automatic tachycardia, after which surgical cryoablation of the left atrial focus was carried out successfully and sinus rhythm was restored. Serial radionuclide angiocardiograms obtained before and after surgery demonstrated a very rapid recovery of left ventricular function to nearly normal within the first month after surgery, followed by further improvement to normal over the next several months. The diagnosis of tachycardia-related cardiomyopathy should be seriously considered in any patient with apparently end-stage dilated cardiomyopathy and persistent resting tachycardia.

Sequence-independent inhibition of in vitro vascular smooth muscle cell proliferation, migration, and in vivo neointimal formation by phosphorothioate oligodeoxynucleotides.

Phosphorothioate oligodeoxynucleotides (PS oligos) are antisense (sequence-specific) inhibitors of vascular smooth muscle cell (SMC) proliferation when targeted against different genes. Recently an aptameric G-quartet inhibitory effect of PS oligos has been demonstrated. To determine whether PS oligos manifest non-G-quartet, non-sequence-specific effects on human aortic SMC, we examined the effects of S-dC28, a 28-mer phosphorothioate cytidine homopolymer, on SMC proliferation induced by several SMC mitogens. S-dC28 significantly inhibited SMC proliferation induced by 10% FBS as well as the mitogens PDGF, bFGF, and EGF without cytotoxicity. Moreover, S-dC28 abrogated PDGF-induced in vitro migration in a modified micro-Boyden chamber. Furthermore, S-dC28 manifested in vivo antiproliferative effects in the rat carotid balloon injury model. S-dC28 suppressed neointimal cross-sectional area by 73% and the intima/media area ratio by 59%. Therefore, PS oligos exert potent non-G-quartet, non-sequence-specific effects on in vitro SMC proliferation and migration as well as in vivo neointimal formation.