Role of inflammation and metalloproteinases in plaque disruption and thrombosis

Numerous pathological, clinical, angiographic and angioscopic studies have demonstrated that acute coronary syndromes (unstable angina, acute myocardial infarction and ischemic sudden death) are most frequently the consequence of plaque disruption (plaque rupture or superficial plaque erosion) and consequent coronary thrombosis. Several serial angiographic studies have demonstrated that nearly 60-70% of acute coronary syndromes evolve from mildly to moderately obstructive atherosclerotic plaques. Coronary plaque disruption appears to be a function of both the composition of the plaque (plaque vulnerability ) as well as extrinsic triggers that may precipitate plaque disruption in a vulnerable plaque. Vulnerability for plaque disruption appears to be largely determined by the size of the lipid-rich atheromatous core, the thickness of the fibrous cap covering the core, and the presence of ongoing inflammation within and underneath the cap. Inflammatory cells may play a critical role in plaque disruption through the elaboration of matrix degrading metalloproteinases or MMPs (collagenases, gelatinases, stromelysins and matrilysin) and by inhibition of function and survival of matrix-synthesizing smooth muscle cells. Inflammatory cells may also play a critical role in triggering thrombosis following plaque disruption through the tissue factor pathway. In addition, stresses resulting from hemodynamic and mechanical forces may precipitate plaque disruption, particularly at points where the fibrous cap is weakest, such as at its shoulders. The degree of thrombosis following plaque disruption is determined by the thrombogenicity of the disrupted plaque, disturbed local rheology and systemic thrombotic-thrombolytic milieu. Surges in sympathetic activity provoked by sudden vigorous exercise, emotional stress -- including anger, or cold weather, may also trigger plaque disruption. These observations have led to the concept of plaque stabilization as a new clinical strategy for the prevention of acute coronary syndromes. Plaque stabilization can be achieved through pharmacologic and lifestyle-modifying interventions that reduce vulnerability to plaque disruption by altering plaque composition and/or inflammatory activity within the plaque.

Effects of clopidogrel, aspirin and combined therapy in a porcine ex vivo model of high-shear induced stent thrombosis

AIMS

Use of ticlopidine in coronary stenting is limited by delayed onset of action. We studied the effects of clopidogrel, a rapidly acting analog of ticlopidine alone, and in combination with aspirin, in inhibiting stent thrombosis.

METHODS

Unpolished nitinol stents were deployed in a porcine ex vivo arteriovenous shunt and exposed to flowing arterial blood at a shear rate of approximately 1500. s-1. Stent thrombus, platelet aggregation and bleeding times were measured at baseline and after treatment.

RESULTS

Intravenous clopidogrel produced a rapid (within 30 min) and dose-dependent inhibition of stent thrombosis, with 87% reduction at a dose of 10 mg.kg-1 (P < 0.001). Aspirin alone (10 mg.kg-1) was minimally effective (20% inhibition P > 0.05) in inhibiting stent thrombosis. Combined treatment with clopidogrel and aspirin produced 95-98% inhibition of stent thrombosis, even at low doses of clopidogrel (2.5-5.0 mg.kg-1) (P < 0.0001). At effective doses both clopidogrel and combined therapy produced significant prolongation of bleeding time (P < 0.05) and inhibition of platelet aggregation (P < 0.05).

CONCLUSION

Clopidogrel, either alone or combined with aspirin, may have a potential role in preventing stent thrombosis in high-risk clinical situations.

An animal model to study local oxidation of LDL and its biological effects in the arterial wall

Oxidized LDL (oxLDL) is present in atherosclerotic lesions and is believed to play a key role in atherogenesis. Mainly on the basis of cell culture studies, oxLDL has been shown to produce many biological effects that influence the atherosclerotic process. To study LDL oxidation in vivo, we have established a model in which Sprague-Dawley rats are given a single injection of unmodified human LDL (> or = 4 mg/kg body weight). Within 6 hours, an accumulation of apolipoprotein B and epitopes present on oxLDL are detected in the arterial endothelium and media. The presence of oxLDL is associated with activation of the transcription factor nuclear factor-kappaB in the endothelium as well as endothelial expression of intercellular adhesion molecule-1. Injection of LDL enriched with the antioxidant probucol resulted in arterial accumulation of apolipoprotein B, but the expression of oxLDL-specific epitopes was reduced at 24 hours. Thus, this simple model has the potential to analyze the mechanisms behind and biological effects of LDL oxidation in vivo.

Remnant lipoprotein cholesterol and triglyceride reference ranges from the Framingham Heart Study

Remnants of triglyceride-rich lipoproteins of both intestinal and liver origin are considered atherogenic, but they have been difficult to isolate and measure. An assay has been developed that allows the measurement of remnant-like particle cholesterol (RLP-C) and triglyceride (RLP-TG). RLP-C and RLP-TG concentrations were measured in >3000 fasting plasma samples obtained from participants in exam cycle 4 of the Framingham Offspring Study and stored at -80 degrees C. After exclusions, comparisons were made for 2821 samples (1385 women, 1436 men; mean age, 52 years). For women, the mean RLP-C and RLP-TG values were 0.176 +/- 0.058 mmol/L (6.8 +/- 2.3 mg/dL) and 0.204 +/- 0.159 mmol/L (18.1 +/- 14.1 mg/dL), respectively; for men, the mean values were 0.208 +/- 0.096 mmol/L (8.0 +/- 3.7 mg/dL) and 0.301 +/- 0.261 mmol/L (26.7 +/- 23.1 mg/dL), respectively. Women had significantly lower RLP-C and RLP-TG values (P <0.0001) than men; premenopausal women had significantly lower values than postmenopausal women (P <0.0001); and younger subjects (<50 years) had significantly lower values than older individuals (P <0.0001). The 75th percentile values for RLP-C and RLP-TG were 0.186 mmol/L (7.2 mg/dL) and 0.225 mmol/L (19.9 mg/dL), respectively, for women, and 0.225 mmol/L (8.7 mg/dL) and 0.346 mmol/L (30.6 mg/dL) for men. These data provide reference ranges for use in the evaluation of RLP-C and RLP-TG as potential indicators of risk for coronary heart disease.

Therapeutic Concentrations of Heparin Augment Platelet Activation at the Time of Coronary Angiography

Background: Besides its anticoagulant effects, heparin is known to alter platelet (PLT) function. We examined the effects of unfractionated heparin on PLT function in patients with stable coronary artery disease (CAD). Methods and Results: PLT function was evaluated by whole-blood flow cytometry to detect PLT CD62 expression and by impedance aggregometry to assess the platelet aggregation (PA) before and after bolus intravenous administration of low-dose heparin (2713 +/- 1231 U) in 16 patients undergoing coronary angiography (group 1) and high-dose heparin (7937 +/- 2414 U) in 16 patients undergoing coronary angioplasty (group 2). Activated clotting time (ACT) and plasma antifactor-Xa heparin levels also were measured. Heparin increased PLT CD62 expression, which was significantly more pronounced in group 1 patients with plasma heparin levels less than 0.7 U/mL and ACT of 222 +/- 52 seconds compared with group 2 patients with heparin levels greater than 0.7 U/mL and ACT of 365 +/- 86 seconds (8 +/- 9 v -1 +/- 4% change in resulting PLTs, P =.01, and 11 +/- 12 v 1 +/- 6% increase in adenosine diphosphate (ADP) [5 µM]-stimulated PLTs, P =.02). Heparin produced a slight increase in PA in group 1 patients (1.4 +/- 5.3 ohms) as compared with the group 2 patients, where it significantly suppressed PA (-3.0 +/- 5.3 ohms, P.05 v group 1). A strong and statistically significant negative correlation between change in platelet CD62 expression and heparin concentration was observed in group 1 patients (r = -.5, P =.05, -ADP; r = -.65, P =.006, +ADP), whereas this relationship was weak and did not reach statistical significance in group 2 patients (r = -0.4, P =.2, -ADP; r =.11, P = 0.9; +ADP). Conclusion: Bolus administration of intravenous heparin augmented PLT activation in patients at clinically relevant anticoagulant concentrations (<0.7 U/mL). These findings may have implications for optimal dosing strategy for heparin as an antithrombotic agent in clinical situations characterized by platelet-dependent thrombotic events.

Effects of recombinant apolipoprotein A-I(Milano) on aortic atherosclerosis in apolipoprotein E-deficient mice

BACKGROUND

We previously reported marked inhibitory effects of recombinant apolipoprotein (apo) A-I(Milano)/phospholipid complex (A-I[Milano]/PC) on neointimal lesions in balloon-injured iliofemoral arteries of hypercholesterolemic rabbits. In this study, we tested the hypothesis that apo A-I(Milano)/PC would inhibit aortic atherosclerosis in apo E-deficient mice.

METHODS AND RESULTS

Thirty-five apo E-deficient mice fed a high-cholesterol diet were included in the study. Control mice were killed at 20 (n=8) or 25 (n=7) weeks. Treated mice received 18 injections of either 40 mg/kg apo A-I(Milano)/PC (n=15) or PC only (n=5) intravenously every other day from 20 weeks until death at 25 weeks. Aortic atherosclerosis was identified with Sudan IV staining. Lipid and macrophage contents of the aortic sinus plaques were measured after oil-red O and Mac-1 antibody staining, respectively, and quantified with computed morphometry. In control mice, from 20 to 25 weeks, aortic atherosclerosis increased by 59% (11 +/- 1% versus 17 +/- 5% of the aortic surface, P=.002), and lipid content increased by 45% (22 +/- 8% versus 32 +/- 6% of plaque area, P=.02) without a significant change in macrophage content (10.8 +/- 2% versus 13.2 +/- 6%). Compared with 20-week-old untreated control mice, PC only-treated mice at 25 weeks demonstrated a 32% increase in aortic atherosclerosis (11 +/- 1% versus 15 +/- 4%, P=.01) and an increase in lipid content (22 +/- 8% versus 47 +/- 3%, P<.0001) without a change in macrophage content (10.8 +/- 2% versus 11 +/- 2%). In comparison with 20-week-old untreated control mice, 25-week-old apo A-I(Milano)/PC-treated mice demonstrated no increase in aortic atherosclerosis (11 +/- 1% versus 10 +/- 4%, P=NS), a 40% reduction in lipid content (22 +/- 8% versus 13 +/- 8%, P=.01), and a 46% reduction in macrophage content (10.8 +/- 2% versus 5.8 +/- 2.9%; P=.03). Serum cholesterol levels were markedly elevated in all groups and did not change significantly with apo A-I(Milano)/PC or PC only. In vitro, apo A-I(Milano)/PC stimulated cholesterol efflux from cholesterol-loaded FU5AH hepatoma cell lines in a dose-dependent manner, whereas PC only or PC-free apo A-I(Miano) had no effect.

CONCLUSIONS

Recombinant A-I(Milano)/PC prevented progression of aortic atherosclerosis and reduced lipid and macrophage content of plaques in apo E-deficient mice despite severe hypercholesterolemia. Thus, A-I(Milano)/PC may have a role in inhibiting progression and promoting stabilization of atherosclerosis.

Lipoprotein-like phospholipid particles inhibit the smooth muscle cell cytotoxicity of lysophosphatidylcholine and platelet-activating factor

Oxidation of LDL is associated with degradation of phosphatidylcholine into platelet-activating factor (PAF)-like phospholipids and lysophosphatidylcholine (LPC). Exposure of cultured human smooth muscle cells to PAF and LPC in a concentration of 25 micromol/L was found to result in complete cell death, as assessed by the MTT cytotoxicity assay and cell counting. Addition of 50 microg/mL apolipoprotein A-I- and apolipoprotein A-I(Milano)-containing phospholipid particles completely inhibited this cytotoxicity. Phospholipid complexes alone were almost as effective, whereas free apolipoprotein A-I(Milano) and albumin were without effect, suggesting that the effect was phospholipid dependent. Experiments using [14C]LPC demonstrated that apolipoprotein A-I- and apolipoprotein A-I(Milano)-containing phospholipid particles effectively bind LPC. The results show that HDL-like phospholipid particles effectively inhibit the toxic effect of phospholipids and other lipid-soluble factors. The ability of HDL to inhibit the proinflammatory and toxic effects of phospholipids generated during oxidation of LDL may be responsible for part of the antiatherogenic properties of HDL.

Aortic smooth muscle cells interact with tenascin-C through its fibrinogen-like domain

The extracellular matrix protein tenascin-C is a multidomain protein that regulates cell adhesion. We used two different smooth muscle cell subtypes derived from adult and newborn rat aorta to investigate the interaction of tenascin-C or its various domains with these cells using an adhesion assay. Newborn cells were three times more adherent to tenascin-C than adult cells. Tenascin C-adhering cells remained round, whereas they spread rapidly on a fibronectin substrate. Adhesion assays showed the interaction between tenascin-C and newborn cells to be predominantly RGD-independent. Mg2+ increased newborn cell adhesion to tenascin-C in a concentration-dependent manner, whereas Ca2+ had no effect. To analyze the structure-function relationships of different domains of tenascin-C, we used recombinant full-length fibronectin-like and fibrinogen-like domains and various subdomains corresponding to the alternatively spliced regions of tenascin-C. The cells adhered to the fibrinogen-like domain but not to the fibronectin-like domain or its subdomains. As with the intact tenascin-C molecule, adherent cells remained round, and the Mg2+, but not Ca2+, promoted this interaction. The interaction of cells with the fibrinogen-like region was further mapped to a 30-amino acid peptide located near the carboxyl-terminal part of the tenascin-C molecule. The same 30-amino acid peptide was active in promoting cell migration. Our results provide a basis for understanding the mechanism of interaction of tenascin-C with smooth muscle cells and a framework for isolating membrane binding sites that mediate the cellular responses to this molecule.

Immunization with homologous oxidized low density lipoprotein reduces neointimal formation after balloon injury in hypercholesterolemic rabbits

OBJECTIVES

In this study we tested the hypothesis that immunization with homologous oxidized low density lipoprotein (oxLDL) would inhibit the neointimal response to balloon injury in hypercholesterolemic rabbits.

BACKGROUND

Immunization with homologous oxLDL has been shown to markedly reduce aortic atherosclerosis in LDL receptor-deficient as well as cholesterol-fed rabbits; however, the effect of this strategy on the balloon injury-induced neointimal lesion is unknown.

METHODS

New Zealand White rabbits were immunized with 280 microg of homologous native LDL (n = 5), copper-oxidized LDL (n = 5) or phosphate buffer as control (n = 5) and fed a 1% cholesterol diet. Rabbits were reimmunized after 3 weeks, and balloon injury of the right ileofemoral artery was performed 1 week later. Four weeks after balloon injury, rabbits were killed, and the neointimal lesion area was measured by computerized morphometry after perfusion fixation of the arteries. Circulating antibodies against oxLDL were measured by enzyme-linked immunosorbent assay.

RESULTS

In comparison with the control animals, those immunized with oxLDL had a 58% reduction in the neointimal area (0.53 +/- 0.13 vs. 1.27 +/- 0.26 mm2; p = 0.01). The group immunized with native LDL had a 19% reduction in the neointimal area compared with the control group (p = NS). Circulating cholesterol levels and antibody titers against oxLDL were comparable in the three groups. There was a trend toward reduced immunoreactivity for T cells and oxLDL in the neointima of oxLDL-immunized animals.

CONCLUSIONS

Hypercholesterolemic rabbits immunized with homologous oxLDL have a markedly reduced neointimal area after balloon injury despite severe hypercholesterolemia. Together with previous work, these data suggest that an immunization strategy (vaccination) against atherosclerosis and restenosis warrants further investigation.

Plaque disruption and coronary thrombosis: new insight into pathogenesis and prevention

Clinical and pathologic studies have confirmed that disruption or superficial erosion of atherosclerotic plaque is the major cause of coronary thrombosis, which is the primary mechanism responsible for acute coronary syndromes of unstable angina, acute myocardial infarction, and sudden cardiac death. Serial angiographic studies have shown that nearly 60-70% of acute coronary syndromes evolve from mildly to moderately obstructive atherosclerotic plaques. The risk of plaque disruption appears to be a function of both plaque vulnerability (intrinsic factors) and extrinsic triggers, and is determined largely by the size of the lipid-rich atheromatous core, the thickness of the fibrous cap covering the core, and the presence of ongoing inflammation within and underneath the cap. Hemodynamic or mechanical stresses may precipitate plaque disruption, particularly in places where the fibrous cap is weakest, such as the shoulders. The degree of thrombosis following plaque disruption depends on the thrombogenicity of the disrupted plaque, the disturbed local rheology, and the systemic thrombotic-thrombolytic milieu. Surges in sympathetic activity (such as those provoked by sudden vigorous exercise, emotional stress, or cold weather) may also trigger plaque disruption. These observations have led to the concept of plaque stabilization as a new strategy for the prevention of acute coronary syndromes. Plaque stabilization can be achieved through pharmacologic and lifestyle-modifying interventions that alter plaque composition and/or inflammatory activity within the plaque and thus reduce its vulnerability to disruption.

Prospective validation of a composite end point in thrombolytic trials of acute myocardial infarction (TIMI 4 and 5). Thrombosis In Myocardial Infarction

Although the use of composite end points in clinical trials has increased in recent years, few data are available on the validity of such an approach. In the Thrombolysis In Myocardial Infarction (TIMI) 4 and 5 trials, we set out to validate prospectively the nonfatal components of the "unsatisfactory outcome" end point. This end point consisted of the in-hospital occurrence or observation of new-onset severe congestive heart failure/shock, left ventricular ejection fraction <40% (or <30% for patients with prior myocardial infarction), reinfarction, reocclusion by sestamibi perfusion imaging, TIMI flow grade <2 at 90 minutes or 18 to 36 hours, intracranial hemorrhage, major spontaneous hemorrhage, or anaphylaxis. Among 576 patients in TIMI 4 and 5 with 1-year follow-up, a nonfatal unsatisfactory outcome end point was reached in hospital in 45% of patients. Compared with patients without such an end point, patients with an end point had a relative risk of 1-year mortality of 2.5 (95% confidence interval 1.4 to 5.6, p = 0.001). For individual components, new-onset severe congestive heart failure/shock had a relative risk of 4.6 (p = 0.001), left ventricular ejection fraction <40% had a relative risk of 3.5 (p = 0.006), recurrent myocardial infarction had a relative risk of 2.2 (p = 0.047), and TIMI flow grade <2 at 90 minutes had a relative risk of 2.2 (p = 0.005). Our findings show that these nonfatal in-hospital end points and the composite end point are associated with an increased risk of 1-year mortality and as such are valid predictive survival markers for use in clinical trials.

Lipid lowering versus revascularization: an idea whose time (for testing) has come

There is strong evidence that revascularization does not prevent myocardial infarction in patients with stable coronary artery disease (CAD). The anatomic basis for this counterintuitive conclusion seems to be that most myocardial infarctions occur at sites that did not previously exhibit an angiographically significant stenosis. These angiographic observations are further supported by thallium studies in stable CAD that demonstrate that the site of stress-induced ischemia is frequently not the site of subsequent myocardial infarction. Since both coronary artery bypass graft surgery and percutaneous transluminal coronary angioplasty are directed at more severe coronary stenoses, we are led to the remarkable conclusion that angiography does not identify, and consequently revascularization therapies do not treat, the lesions that lead to myocardial infarction. The pathology of coronary atherosclerosis provides the basis for understanding why revascularization does not prevent infarction: unstable lesions that cause infarction are not necessarily severely stenotic, and stenotic lesions are not necessarily unstable. In contrast to revascularization, lipid lowering reduces the rate of myocardial infarction by approximately 30% over a period of 5 years. Thus, we might postulate that lipid lowering is the more effective therapy for both prevention of acute myocardial infarction and long-term survival. The health policy and economic implications of this viewpoint, should it emerge in the management of coronary heart disease, are clearly substantial. Consequently, the relative roles of lipid-lowering therapy and revascularization, both alone and together, must now be determined. It is an idea whose time--for testing--has come.

Local Delivery of an Ultra-short-acting Nitric Oxide-releasing Compound, DMHD/NO, Is Highly Effective in Inhibiting Acute Platelet-Thrombus Formation on Injured Arterial Strips

BACKGROUND: Nitric oxide (NO) plays an important role in modulating platelet-vessel wall interaction following vascular injury. We exampled the effects of local infusion of an ultra-short-acting NO-releasing compound: NO adduct of N, N'-dimethylhexanediamine (DMHD/NO), sodium nitroprusside, intravenous nitroglycerin, and aspirin on acute platelet-thrombus formation under conditions of high-shear blood flow in a rabbit extracorporeal perfusion model. MATERIALS AND METHODS: Strips of porcine aortic media were perfused in a Badimon chamber with arterial blood from 20 New Zealand White rabbits for 10 minutes at a shear rate of 1700 s(-1). Thrombus formation was quantified by morphometric analysis of thrombus area. Effects on collagen-induced platelet aggregation, blood pressure, bleeding time, and activated clotting time were also examined. RESULTS: DMHD/NO inhibited thrombus area and platelet aggregation in a dose-dependent manner with a 90% reduction in thrombus area (0.018 +/- 0.039 vs 0.215 +/- 0.085 mm(2)/mm control, P <.001) and a 50% reduction in platelet aggregation (4.8 +/- 4.4 vs 9.9 +/- 4.1 Omicron control, P =.04) at the highest dose of 1.0 nM/kg and 100 µM/L, respectively, without any effects on blood pressure, bleeding time, or activated clotting time. In contrast, equimolar concentrations of sodium nitroprusside and intravenous nitroglycerin had significantly reduced effects on thrombus area compared to DMHD/NO and were associated with significant reductions in blood pressure and prolongation of bleeding time. Aspirin had no effect on thrombus area at 1 µM/kg but reduced thrombus area and prolonged bleeding time at 2 and 5 µM/kg. CONCLUSIONS: Local delivery of DMHD/NO produced a 90% inhibition of experimental acute platelet-thrombosis under high-shear flow conditions without producing adverse systemic hemodynamic or hemostatic effects. Thus, inhibition of thrombus formation by local delivery of a rapidly acting NO donor may be an effective strategy for prevention of arterial injury-induced thrombosis.

New insights into the pathogenesis and prevention of acute coronary syndromes

Several recent studies have shown that 60-70% of coronary occlusions that cause acute coronary syndromes (such as unstable angina, myocardial infarction, or sudden ischemic death) evolve from atherosclerotic plaques that are only mildly to moderately obstructive. Numerous studies have demonstrated that coronary thrombosis, the immediate cause of acute coronary syndromes, is a consequence of plaque disruption. Most thrombotic events are related to deep plaque fissure, while superficial plaque erosion is the cause in a significant minority of cases. Thus, the mechanisms by which stable coronary artery disease (CAD) evolves into an unstable and potentially lethal acute coronary syndrome are related to plaque disruption and thrombosis. The vulnerability of a plaque to disruption appears to be determined by the presence of a large lipid-rich core, a thin fibrous cap, and an inflammatory cellular infiltrate, rather than by the size of the plaque or the severity of stenosis caused by a plaque before disruption. In addition to plaque disruption and thrombosis, enhanced vasoconstriction--a characteristic feature of CAD and dyslipidemia-may contribute to the clinical manifestations of CAD. Angiographic studies have demonstrated that risk factor modification produces a disproportionately greater reduction in ischemic clinical events than in anatomic regression of plaque, suggesting "plaque stabilization" may be the major mechanism of such clinical benefit. The relatively rapid attenuation of endothelial-mediated vasomotor dysfunction with the treatment of dyslipidemia lends credence to this concept.

Does the presence and site of myocardial ischemia on perfusion scintigraphy predict the occurrence and site of future myocardial infarction in patients with stable coronary artery disease?

In 47 patients who had undergone myocardial scintigraphy, reversible perfusion abnormality was detected in only 28 segments (60%) that were the site of future acute myocardial infarction.

Nuclear factor-kappaB activity and arterial response to balloon injury

We studied the effect of arterial balloon injury on nuclear factor-kappaB (NF-kappaB) mobilization and ICAM-1 expression in untreated rats and rats treated with aspirin. Baseline NF-kappaB nuclear binding in smooth muscle cells (SMC) increased two-fold within 6 h after balloon injury. The binding returned to baseline 3 days after injury. Consistently nuclear staining of p65 active subunit increased in the medial SMC following balloon injury. There was no baseline ICAM-1 expression. Within 3 days after balloon injury there was marked medial ICAM-1 expression, that localized to neointima 7 days after injury and to regrowing endothelial cells 14 days after injury. Treatment with aspirin inhibited NF-kappaB nuclear translocation and binding and was associated with reduction of ICAM-1 expression, SMC proliferation and neointimal thickening following balloon injury. These data suggest that transient mobilization of NF-kappaB in vascular SMC after balloon injury mediates ICAM-1 expression and is involved in arterial response to balloon injury.

Clinical dysautonomia in diabetes mellitus--a study with seven autonomic reflex function tests

Thirty-eight patients of NIDDM, 12 of IDDM and 10 healthy age matched controls were subjected to seven standardised autonomic reflex function tests. A scoring criteria was utilised for diagnosing and grading the severity of dysautonomia. Eight patients of IDDM and 24 of NIDDM had dysautonomia. One-third of the patients in each group had grade IV autonomic dysfunction. Severity of autonomic dysfunction was directly related to the duration of disease in NIDDM whereas in IDDM this relation was not seen. Peripheral neuropathy was almost always associated with dysautonomia in NIDDM. On the contrary, in IDDM dysautonomia was independent of peripheral neuropathy. Charcot's arthopathy, dysphagia, constipation and nocturnal diarrhea were always associated with evidence of dysautonomia. Other symptoms viz. gustatory sweating, postural dizziness and impotence did not necessarily indicate dysautonomia.

Using serum cholesterol as a screening test for preventing coronary heart disease: the five fundamental flaws of the American College of Physicians Guidelines

The guidelines ignore the common catastrophic first presentation of coronary disease, the powerful predictive value of serum cholesterol in young persons, the effectiveness of cholesterol-lowering interventions, the low cost of effective dietary modification, and the effectiveness of lipid lowering in women and in the elderly.

Direct effects of somatostatin analog octreotide on insulin-like growth factor-I in the arterial wall

Local vascular expression and action of insulin-like growth factor-I (IGF-I) appear to be important in the biologic events that follow arterial wall injury. Octreotide, a long-acting somatostatin analog, is a potent inhibitor of the growth hormone/IGF-I axis. We examined the effects of octreotide on the vascular IGF-I and IGF-binding proteins (IGFBP), gene regulation, smooth muscle cell proliferation, and neointimal thickening after arterial wall injury. Treatment with octreotide selectively decreased IGF-I mRNA expression in normal rat arteries by 70% and prevented the induction of the IGF-I gene after balloon injury. Because up-regulation of platelet-derived growth factor-A gene was not affected, and because there was no change in plasma growth hormone, IGF-I, and glucagon levels, it appears that this effect is selective and mediated locally. Of the IGFBP, IGFBP-4 was modestly up-regulated after balloon injury, whereas treatment with octreotide had no effect on IGFBP-4 expression. The inhibitory effects of octreotide on vascular IGF-I were associated with a decrease in the number of proliferating cell nuclear antigen-positive cells and an up to 90% reduction in neointimal thickening after balloon injury in a dose-dependent fashion.

Effects of GP IIb/IIIa receptor monoclonal antibody (7E3), heparin, and aspirin in an ex vivo canine arteriovenous shunt model of stent thrombosis

BACKGROUND

Thrombosis is an important limitation of metallic coronary stents, especially in smaller vessels in which shear rates are high. Monoclonal antibody to platelet glycoprotein IIb/IIIa receptor (7E3) has been shown to inhibit shear-induced platelet aggregation. In this study, we compared the effects of 7E3, heparin, and aspirin on stent thrombosis in an ex vivo arteriovenous shunt model of high-shear blood flow.

METHODS AND RESULTS

An ex vivo arteriovenous shunt was created in 10 anesthetized dogs. Control rough-surface slotted-tube nitinol stents (n = 72) expanded to 2 mm in diameter in a tubular perfusion chamber were interposed in the shunt and exposed to flowing arterial blood at a shear rate of 2100s-1 for 20 minutes. The animals were treated with intravenous murine 7E3 (Fab')2 (0.2, 0.4, and 0.8 mg/kg), heparin (100 U/kg), or aspirin (10 mg/kg). Effects of the test agents on thrombus weight, platelet aggregation, platelet P-selectin expression, bleeding time, and activated clotting time (ACT) were quantified. 7E3 reduced stent thrombosis by 95% (20 +/- 1 to 1 +/- 1 mg, P < .001) and platelet aggregation by 94% (14 +/- 2 to 1 +/- 1 omega, P < .001) at the highest dose (0.8 mg/kg). 7E3 significantly prolonged bleeding time but had no effect on ACT and platelet P-selectin expression. Heparin prolonged ACT but had no significant effect on stent thrombosis or platelet aggregation. Aspirin, although it inhibited platelet aggregation by 65%, had no effect on stent thrombosis (19 +/- 2 versus 20 +/- 1 mg in controls).

CONCLUSIONS

7E3 produced a dose-dependent inhibition of acute stent thrombosis under high-shear flow conditions. Stent thrombosis was resistant to heparin and aspirin. Thus, 7E3 may be an effective agent for preventing stent thrombosis.