Biomedical subjects
Publications and source records attributed to David C Sane.
We evaluated the frequency and importance of anemia in 137 patients with heart failure and a normal ejection fraction (diastolic heart failure). We found that anemia is common in these patients and is associated with greater elevations in serum B-type natriuretic peptide, more severe diastolic dysfunction, and a worse prognosis.
The vitamin K-dependent gamma-carboxylation system is responsible for post-translational modification of vitamin K-dependent proteins, converting them to Gla-containing proteins. The system consists of integral membrane proteins located in the endoplasmic reticulum membrane and includes the gamma-carboxylase and the warfarin-sensitive enzyme vitamin K(1) 2,3-epoxide reductase (VKOR), which provides gamma-carboxylase with reduced vitamin K(1) cofactor. In this work, an in vitro gamma-carboxylation system was designed and used to understand how VKOR and gamma-carboxylase work together as a system and to identify factors that can regulate the activity of the system. Results are presented that demonstrate that the endoplasmic reticulum chaperone protein calumenin is associated with gamma-carboxylase and inhibits its activity. Silencing of the calumenin gene with siRNA resulted in a 5-fold increase in gamma-carboxylase activity. The results provide the first identification of a protein that can regulate the activity of the gamma-carboxylation system. The propeptides of vitamin K-dependent proteins stimulate gamma-carboxylase activity. Here we show that the factor X and prothrombin propeptides do not increase reduced vitamin K(1) cofactor production by VKOR in the system where VKOR is the rate-limiting step for gamma-carboxylation. These findings put calumenin in a central position concerning regulation of gamma-carboxylation of vitamin K-dependent proteins. Reduced vitamin K(1) cofactor transfer between VKOR and gamma-carboxylase is shown to be significantly impaired in the in vitro gamma-carboxylation system prepared from warfarin-resistant rats. Furthermore, the sequence of the 18-kDa subunit 1 of the VKOR enzyme complex was found to be identical in the two rat strains. This finding supports the notion that different forms of genetic warfarin resistance exist.
Antiplatelet therapy has been the focus of extensive clinical investigations over the last two decades. A variety of agents and regimens have been advanced for the prevention and treatment of vascular disease. Despite the proven life-saving clinical benefits of inhibiting platelets, this therapy is associated with an increased risk of bleeding. The objective of this study was to determine the risk of hemorrhage in the major classes of antiplatelet agents. Data from clinical trials published 1988-2002 in English were retrieved from MEDLINE, OVID, and CARDIOSOURCE. Only those studies in which patients had clinical follow-up for at least 1 month and in which a full description of hemorrhagic complications was reported were included. Information on sample size, study design, duration, agent, patient characteristics, and bleeding severity was independently and blindly reviewed. Data from 51 clinical trials with a total of 338,191 patients were analyzed. The antiplatelet agents were divided into 6 groups: aspirin (ASA) < 100 mg; ASA > or = 100 mg; dipyridamole, thienopyridines; intravenous and oral GP IIb/IIIa inhibitors. The variance estimate and confidence intervals were calculated for each treatment assignment. Low-dose aspirin and dipyridamole therapy were associated with the lowest risk of bleeding (3.6% and 6.7%, respectively). The highest rate of bleeding complications (44.6%) was associated with the GP IIa/IIIb inhibitors. Despite substantial differences in the reporting patterns of bleeding complications, low-dose ASA and dipyridamole therapy were associated with the lowest risk. Surprisingly, doses of ASA >/= 100 mg caused a relatively high hemorrhagic event rate, which was comparable to that of ADP-receptor blockers. These findings should be considered when using combination antiplatelet and/or anticoagulant therapy with conventional doses of ASA.
Emerging evidence supports a novel view of hypertension as a disease of inadequate or aberrant responses to angiogenic growth factors (AGF). Patients with hypertension have reduced microvascular density, with some evidence supporting a primary role for rarefaction in causing hypertension. Two clinical models have demonstrated a link between inhibition of AGF activity and hypertension. A major side effect of bevacizumab, a monoclonal antibody to vascular endothelial growth factor (VEGF), is hypertension. Pre-eclampsia is accompanied by high circulating levels of soluble VEGF receptor-1, which forms inactive complexes with VEGF and placental growth factor (PlGF). Paradoxically, early studies have demonstrated high circulating levels of AGF in hypertension. Several mechanisms may account for this finding including increased vascular stretch, tissue ischemia, compensatory responses, decreased clearance or a combination of these mechanisms. High AGF in hypertension could contribute to clinical sequelae such as peripheral and pulmonary edema, microalbuminuria, and progression of atherosclerosis. However, a role for altered angiogenesis in the pathogenesis of hypertension or its sequelae has not been established. Novel studies to understand the roles of AGF in hypertensive patients are warranted.
BACKGROUND: We postulated that antibodies to platelet factor 4/heparin complex lead to a heightened inflammatory state, contributing to an increased risk of recurrent thrombotic events. METHODS: We analyzed serum from a subset of patients in the placebo/unfractionated heparin arm of the GUSTO IV-ACS trial who had prior heparin exposure. We selected 109 patients with the 30 day primary endpoint (death, MI or revascularization) and an equal number of controls, excluding patients with thrombocytopenia. Anti-platelet factor 4/heparin antibodies and inflammatory markers (sVCAM-1, sICAM-1, sE-selectin, sP-selectin, us-CRP, IL-6) were measured on serum samples. RESULTS: Patients with anti-PF4/heparin antibodies were more likely to have death or MI (30.4% vs. 11.3%, p = 0.01), or MI (21.7% vs. 6.2%, p = 0.01) than patients who were antibody negative. In a multiple logistic regression model that included inflammatory markers and clinical risk factors, antibody to PF4/heparin was a strong predictor of 30 day MI (odds ratio: 9.0; 95% confidence intervals 2.1-38.6; p < 0.01), with IL-6 being the only other predictor (odds ratio: 1.1; 95% confidence intervals 1.0-1.2; p = 0.03). Antibody positive patients had higher levels of sVCAM-1 (892 +/- 263 microg/l versus 780 +/- 228 microg/l; p = 0.04) and sICAM-1(246 +/- 50 microg/l versus 222 +/- 71microg/l; p = 0.02) than antibody-negative patients. CONCLUSIONS: Antibodies to the platelet factor 4/heparin complex were associated with elevated levels of endothelial but not platelet activation markers, or markers of a systemic inflammatory state. Anti-PF4/heparin antibodies were associated with a 9-fold increased risk of recurrent MI at 30 days. We measured soluble cell adhesion molecules, CRP and IL-6 from 218 non-thrombocytopenic patients, 23 of whom had antibodies to PF4/heparin. Antibody positive patients had higher levels of sVCAM-1 (892 +/- 263 microg/l versus 780 +/- 228 microg/l; p = 0.04) and sICAM-1(246 +/- 50 microg/l versus 222 +/- 71 microg/l; p = 0.02). In a multiple logistic regression model, antibody to PF4/heparin was a predictor of 30 day MI (odds ratio: 9.0; 95% CI: 2.1-38.6; p < 0.01). The presence of antibodies to PF4/heparin, even in the absence of thrombocytopenia, is a stronger predictor of 30 day MI than clinical variables or inflammatory markers.
OBJECTIVE: Regulator of G protein signaling 5 (RGS5), an inhibitor of Galpha(q) and Galpha(i) activation, was recently identified among genes highly expressed in smooth muscle cells (SMCs) of aorta but not vena cava. This finding prompted the hypothesis that RGS5 provides long-term G protein inhibition specific to normal arterial SMC populations and that loss of expression may in turn contribute to arterial disease. METHODS: To test this hypothesis we characterized RGS5 gene expression throughout the vasculature of nonhuman primates to determine whether RGS5 was restricted to arteries in other vascular beds and whether expression was altered in arterial disease. RESULTS: In situ hybridization localized RGS5 message to medial SMCs of peripheral arteries, including carotid, iliac, mammary, and renal arteries, but not accompanying veins. SMCs of many small arteries and arterioles also expressed RGS5, including glomerular afferent arterioles critical to blood pressure regulation. Differential expression persisted in culture, inasmuch as RGS5 message was significantly higher in SMCs derived from arteries than from veins at real-time polymerase chain reaction. It was remarkable that the only major arterial bed lacking RGS5 was the coronary circulation. In atherosclerotic peripheral arteries RGS5 was expressed in medial SMCs, but was sharply downregulated in plaque SMCs. CONCLUSION: These data identify RGS5 as a new member of a short list of genes uniquely expressed in peripheral arteries but not coronary arteries. Persistence of an arterial pattern of RGS5 expression in culture and lack of expression in coronary arteries support a unique SMC phenotype fixed by distinct lineage or differentiation pathways. The association between loss of expression and arterial wall disease has prompted the new hypothesis that prolonged inhibition by RGS5 of vasoactive or trophic G protein signaling is critical to normal peripheral artery function.
INTRODUCTION: Platelets play an important role in the natural history of ischemic stroke, and are known to be activated in the acute phase. Although aspirin reduces risks of myocardial infarction, stroke and cardiovascular death, the extent of platelet action and the effect of aspirin on platelet function in patients recovering from stroke remain unclear. METHODS: We studied 120 individuals divided into three equal groups: aspirin-free patients after ischemic stroke, post-stroke patients receiving aspirin (81-650 mg/daily), and aspirin-free subjects with multiple risk factors for vascular disease. Conventional platelet aggregation induced by 5 microM ADP and 5 microM epinephrine, cartridge-based analyzers (Ultegra, and PFA-100) readings, and expression of CD31, CD41a, CD42b, GPIIb/IIIa activity, CD51/CD61, CD62p, CD63, CD107a, CD154, CD165, formation of platelet-monocyte aggregates, intact (SPAN12), and cleaved (WEDE15) PAR-1 thrombin receptors by flow cytometry were analyzed. RESULTS: There were no differences between aspirin-free post-stroke patients and aspirin-free controls. Although aggregation was slightly higher, 12 out of the 14 receptor analyses, were surprisingly lower in the post-stroke cohort. Aspirin-treated patients exhibited highly significant inhibition of epinephrine-induced aggregation (p=0.0001), prolongation of the closure time (p=0.03), and reduction of the aspirin reactive units (p=0.02) measured by the Ultegra device. In addition, surface platelet expression of thrombospondin (p=0.001), GPIIb/IIIa activity (p=0.04), P-selectin (p=0.03), CD40-ligand (p=0.04), CD165 (p=0.02), the formation of the platelet-monocyte aggregates (p=0.01), and intact epitope of PAR-1 thrombin receptor (p=0.03) were significantly lower in the aspirin-treated group. CONCLUSIONS: Platelets are not activated in aspirin-free patients after ischemic stroke. Platelet function is significantly inhibited in those treated with aspirin when compared with healthy subjects with risk factors for vascular disease. Bleeding complications and hemorrhagic transformations after aggressive antiplatelet regimens could be related to the decreased or normal baseline platelet characteristics in such patients. Further analysis of platelet heterogeneity and its clinical significance remains to be determined in randomized trials.
We present three clinical cases that illustrate some of the key features of the diagnosis and management of immune-mediated heparin-induced thrombocytopenia (HIT). The importance of having a high clinical suspicion for HIT in the appropriate clinical setting is emphasized. Early therapeutic decisions should be based on a clinical diagnosis, with laboratory tests serving as confirmation. Low-molecular-weight and unfractionated heparins are to be strictly avoided in patients with HIT. Identification bracelets or necklaces may be useful to reduce inappropriate administration of these agents to patients with HIT presenting with acute coronary syndromes.
Heparin was first discovered in 1916 and at present is used in more than 12 million patients a year. In the 1950s, several physicians noticed an uncommon paradoxical phenomenon in which heparin appeared to function as a procoagulant instead of an anticoagulant. This phenomenon is now known as the immune-mediated heparin-induced thrombocytopenia (HIT) and thrombosis syndrome (HITTS). Our understanding of this syndrome has evolved over the last 2 to 3 decades, and therapeutic options are arising. This article will focus on the most extensively studied therapy for HIT, which is the class of drugs known as the direct thrombin inhibitors. Specifically, we will focus on the mechanisms by which direct thrombin inhibitors may be useful in this syndrome, the evidence for their use, and the unique characteristics of the two FDA-approved agents in this class, lepirudin and argatroban.
We postulated that patients with recent acute coronary syndromes and antibodies to the platelet factor 4/heparin complex would have an increased risk of myocardial infarction (MI), even in the absence of thrombocytopenia. We analyzed sera from patients enrolled in the placebo/unfractionated heparin arm of the GUSTO IV-ACS trial who had a high likelihood of prior heparin exposure. We selected 109 patients without thrombocytopenia with the 30-day primary endpoint (death, MI, or revascularization) and 109 age-, gender-, and race-matched controls who did not achieve the primary endpoint. Twenty-three of 218 patients (10.6%) had anti-PF4/heparin antibodies. Patients with anti-PF4/heparin were more likely to have death or MI (30.4% vs. 11.3%, p = 0.011) or MI (21.7% vs. 6.2%, p = 0.008) than patients who were negative for the antibody. Antibody-positive patients had higher levels of sVCAM-1 (892 +/- 263 microg/L vs. 780 +/- 228 microg/L; p = 0.04) and sICAM-1 (246 +/- 50 microg/L vs. 222 +/- 71 microg/L; p = 0.02) than antibody-negative patients. In a multiple logistic regression model that included inflammatory markers and clinical risk factors, antibodies to PF4/heparin were a strong predictor of 30-day MI (odds ratio, 9.0; 95% confidence intervals, 2.1 to 38.6; p < 0.01), with IL-6 being the only other predictor (odds ratio, 1.1; 95% confidence intervals, 1.0 to 1.2; p = 0.03). Antibodies to the platelet factor 4/heparin complex are a novel, independent predictor of MI at 30 days in patients presenting with acute coronary ischemic syndromes. Antibodies to PF4/heparin are a stronger predictor of MI than clinical characteristics or inflammation markers.
Valsartan selectively blocks angiotensin II binding to the AT1 receptor. ince platelet activation plays a key role in the pathogenesis of vascular disease, and because AT1 receptors are present on the platelet surface, we assessed the in vitro effects of valsartan and its metabolite, valeryl 4-hydroxy valsartan (V4HV), on platelets in 30 subjects with multiple risk factors for cardiovascular disease. Platelet characteristics in blood samples pretreated and incubated with 10 nmol to 100 micromol concentrations of valsartan and V4HV were assessed by aggregometry, rapid platelet analyzers, and by flow cytometry. Pretreatment of blood with valsartan and V4HV resulted in inhibition of conventional plasma (ADP, P = 0.0001, valsartan; epinephrine, P = 0.0001, V4HV) and whole blood collagen-induced (P = 0.01, valsartan; P =.0001, V4HV) platelet aggregation. Closure time was delayed (P = 0.02, valsartan; P = 0.03, 4VHV), indicating platelet inhibition in whole blood under high shear conditions. Expression of many surface platelet receptors, namely GP IIb/IIIa antigen, and activity, vitronectin, p-selectin, and LAMP-1 was significantly reduced compared with autologous baseline activity. Intensity of platelet-leukocyte formation and other platelet activation markers remained unchanged. Platelet inhibition was not dose dependent and was more potent for 4VHV than valsartan in the therapeutic range.Valsartan and 4VHV exhibited significant in vitro inhibition of human platelets. Their antiplatelet properties, especially more potent activity of the metabolite appear to be independent of those of other antiplatelet agents. Whether valsartan reduces vascular ischemic events via additional pathways of platelet inhibition in patients with myocardial infarction and ischemic stroke requires further clinical research.
BACKGROUND: Both abciximab (AB) and eptifibatide (EP) are approved for use during percutaneous coronary intervention (PCI) but comparative data between the 2 agents are limited. METHODS: We compared in-hospital and 30-day outcomes of contemporary 495 consecutive PCIs performed by a single operator between July 2001 and November 02 with AB and EP (242 with AB and 253 with EP). Cardiogenic shock patients who underwent a second procedure within 30 days from their first procedure were excluded. Selection of glycoprotein IIb/IIIa was at the operator's discretion. The initial 444 cases were performed with unfractionated heparin and the last 51 with bivalirudin. RESULTS: AB cases comprised a higher risk group with more patients with diabetes, peripheral vascular disease, ST-elevation myocardial infarction and renal failure (p<0.05 for each) and more rotablator use and longer lesions (p<0.01 for each). AB was associated with less in-hospital (4.6 versus 12.3%; OR: 0.34; 95% CI: 0.17-0.7; p=0.004) as well as 30-day (5.5 versus 14%; OR: 0.37; 95% CI: 0.19-0.71; p=0.003) major adverse cardiac events (sum of death, MI, urgent revascularization, all bleeding and stroke). CONCLUSION: Despite its use in higher risk PCI patients, AB resulted in superior short-term outcomes compared with EP. Our data suggest that significant efficacy differences may exist between these 2 agents and that a randomized comparison is warranted.
OBJECTIVE: To summarize the structure, function, and regulation of matrix metalloproteinases (MMPs) and to review the literature to date on their potential role in the pathogenesis of acute coronary syndromes. METHODS: A recursive strategy starting with a Medline Search for primary articles in the last decade, followed by identification of additional articles of interest among the cited literature in the primary articles, followed by identification of additional articles of interest cited in the secondary articles. RESULTS: MMPs play a central role in many fundamental processes in human health and disease. In vitro evidence suggests that MMP activity may facilitate atherosclerosis, plaque destabilization, and platelet aggregation. Limited evidence from clinical studies supports a role of MMPs in the development of acute coronary syndromes. CONCLUSIONS: MMP activity likely contributes to the development of acute coronary syndromes and may be an important therapeutic target for future drug development.
Erythropoietin is a hypoxia-induced hormone that is essential for normal erythropoiesis. The production of recombinant human erythropoietin (rHuEpo) has revolutionized the treatment of anemia associated with chronic renal failure and chemotherapy, and has been used as prophylaxis to prevent anemia after surgery. The erythropoietin receptor is widely distributed in the cardiovascular system, including endothelial cells, smooth muscle cells and cardiomyocytes. Epo has potentially beneficial effects on the endothelium including anti-apoptotic, mitogenic and angiogenic activities. On the other hand, some reports suggest that rHuEpo may have pro-thrombotic or platelet-activating effects. Hypertension develops in 20-30% of renal patients treated with rHuEpo. Many patients with heart failure have anemia. Despite some potential adverse effects, early studies in heart failure patients with anemia suggest that rHuEpo therapy is safe and effective in reducing left ventricular hypertrophy, enhancing exercise performance and increasing ejection fraction. Further studies are warranted to define the role of rHuEpo in chronic heart failure and other cardiovascular settings.
VEGF, an endothelial-specific mitogen, is an important tumor angiogenesis growth factor. The major receptor for VEGF on endothelial cells is KDR. We hypothesized that an intrabody could bind newly synthesized KDR and block receptor transport to the cell surface, thereby inhibiting important VEGF effects. We expressed a single chain antibody (p3S5) to KDR with or without the endoplasmic reticulum (ER) retention signal (KDEL), using either a plasmid (p3S5-HAK) or a tet-off adenoviral system (Ad-HAK). Plasmid-mediated expression of the tethered intrabody significantly reduced KDR expression (from 82.5+/-12.5% to 27.9+/-13.6% of cells; P<0.01) and thymidine incorporation in successfully transfected cells. Ad-HAK infection resulted in intrabody expression in >90% of human umbilical vein endothelial cells (HUVECs), producing marked (80%) apoptosis at 48 h postinfection. The intrabody was essential for these effects, as confirmed by inhibiting its expression with doxycycline or by expressing irrelevant genes (lacZ, GFP). Cell death was dependent on KDR, because Ad-HAK infection of cell lines with minimal or no KDR had little effect on cell viability. Infected HUVECs were unable to form tubes on Engelbreth Holm-Swarm (EHS) tumor gel matrix. These results demonstrate the potential for development of an intrabody-based strategy to block angiogenesis and prevent tumor growth.
BACKGROUND: We postulated that antibodies to platelet factor 4/heparin complex might contribute to recurrent ischemic events in patients with acute coronary syndrome. METHODS AND RESULTS: We analyzed serum from patients enrolled in the placebo/unfractionated heparin arm of the GUSTO IV-ACS trial who had high likelihood of prior heparin exposure. We selected 109 patients without thrombocytopenia with the 30-day primary end point (death, myocardial infarction [MI], or revascularization) and 109 age-, gender-, and race-matched controls who did not achieve the primary end point. An ELISA for anti-platelet factor 4/heparin antibodies was performed using 48-hour serum samples. The analyses were done by blinded investigators, and the results were correlated with clinical outcomes. Twenty-three of 218 patients (10.6%) had anti-PF4/heparin antibodies. Patients with anti-PF4/heparin antibodies were more likely to have death or MI (30.4% versus 11.3%, P=0.011) or MI (21.7% versus 6.2%, P=0.008) than patients who were negative for the antibody. After multiple logistic regression analysis, anti-PF4/heparin antibodies remained a predictor of 30-day death or MI (odds ratio, 4.0; 95% CI, 1.4 to 11.3; P=0.0093) and MI (odds ratio, 4.6; 95% CI, 1.4 to 15.0; P=0.0108). The antibody was not associated with the composite end point (death, MI, or revascularization) or with death or revascularization alone. CONCLUSIONS: Antibodies to the platelet factor 4/heparin complex are a novel, independent predictor of myocardial infarction at 30 days in patients presenting with acute coronary ischemic syndromes. This finding may explain the previous association between thrombocytopenia and adverse events in patients with acute coronary syndrome and may have important implications for the choice of anticoagulant regimens.
Aggrenox is a novel combination of 25 mg of aspirin with 200 mg of sustained release dipyridamole. In a recent large trial (ESPS-2), Aggrenox was twice as effective for secondary stroke prevention as either aspirin or dipyridamole alone, suggesting superior platelet inhibition for combination therapy. We sought to compare the time course of platelet inhibition with Aggrenox compared with escalating doses of non-enteric coated aspirin. Data from 10 healthy volunteers were analyzed. Fasting subjects sequentially ingested aspirin in the following order: 325 mg, 81 mg, 25 mg, and then one pill of Aggrenox after a 3-week interval for aspirin washout. Platelet function was assessed at baseline, 15, 30, 60, and 120 min post-medication with 5 microM epinephrine and 5 microM ADP using conventional aggregometry. Aspirin provided significant (P < 0.01) reduction of platelet aggregation at 15 min post 325 mg, 30 min post 81 mg, and unexpectedly within 60 min after taking 25 mg of aspirin. A single pill of Aggrenox also inhibited platelet aggregation within 1 hr after administration. Aspirin inhibits platelets remarkably fast. Both Aggrenox and a matching dose of aspirin (25 mg) exhibit significant antiplatelet properties within 60 min after ingestion. These findings could be relevant for the optimal balance between the reduction of vascular events via sufficient and rapid platelet inhibition and low risk of bleeding complications associated with the Aggrenox therapy.
The adverse long-term effects of diabetes mellitus have been well described and involve many organ systems. While diabetes management has largely focused on control of hyperglycemia, the presence of abnormalities of angiogenesis may cause or contribute to many of the clinical manifestations of diabetes. When compared with non-diabetic subjects, diabetics demonstrate vascular abnormalities of the retina, kidneys, and fetus. Diabetics have impaired wound healing, increased risk of rejection of transplanted organs, and impaired formation of coronary collaterals. In each of these conditions, and possibly in diabetic neuropathy as well, abnormalities of angiogenesis can be implicated in the pathogenesis. A perplexing feature of the aberrant angiogenesis is that excessive and insufficient angiogenesis can occur in different organs in the same individual. In this review, the clinical features, molecular mechanisms, and potential therapeutic options of abnormal angiogenesis in diabetes will be reviewed.