Who's on first? Does hypertension in type I diabetics result from nephropathy or metabolic alterations?
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Antihypertensive Agents↗
Biomedical subjects
M S Runge
Publications and source records attributed to M S Runge.
Randomized comparison of a strategy of predischarge coronary angiography versus exercise testing in low-risk patients in a chest pain unit: in-hospital and long-term outcomes.
OBJECTIVES: This randomized trial compared a strategy of predischarge coronary angiography (CA) with exercise treadmill testing (ETT) in low-risk patients in the chest pain unit (CPU) to reduce repeat emergency department (ED) visits and to identify additional coronary artery disease (CAD). BACKGROUND: Patients with chest pain and normal electrocardiograms (ECGs) have a low likelihood of CAD and a favorable prognosis, but they often seek repeat evaluations in EDs. Remaining uncertainty regarding their symptoms and diagnosis may cause much of this recidivism. METHODS: A total of 248 patients with no ischemic ECG changes triaged to a CPU were randomized to CA (n = 123) or ETT (n = 125). All patients had a probability of myocardial infarction < or =7% according to the Goldman algorithm, no biochemical evidence of infarction, the ability to exercise and no previous documented CAD. Patients were followed up for > or =1 year and surveyed regarding their chest pain self-perception and utility of the index evaluation. RESULTS: Coronary angiography showed disease (> or =50% stenosis) in 19% and ETT was positive in 7% of the patients (p = 0.01). During follow-up (374+/-61 days), patients with a negative CA had fewer returns to the ED (10% vs. 30%, p = 0.0008) and hospital admissions (3% vs. 16%, p = 0.003), compared with patients with a negative/nondiagnostic ETT. The latter group was more likely to consider their pain as cardiac-related (15% vs. 7%), to be unsure about its etiology (38% vs. 26%) and to judge their evaluation as not useful (39% vs. 15%) (p < 0.01 for all comparisons). CONCLUSIONS: In low-risk patients in the CPU, a strategy of CA detects more CAD than ETT, reduces long-term ED and hospital utilization and yields better patient satisfaction and understanding of their condition.
Adult↗
New tricks for old dogs: nonthrombotic effects of thrombin in vessel wall biology.
Thrombin is a serine protease that potently activates platelets and catalyzes the conversion of fibrinogen to fibrin. Thrombin also exerts direct effects on vascular cells, such as smooth muscle cells, via interactions with members of the protease-activated receptor family. Evidence in several animal models implicates thrombin-mediated signaling events in the response to injury that typifies vascular lesion formation in atherosclerosis and restenosis. In this review, we examine the activation of protease-activated receptors by thrombin, the downstream signaling events mediated by these receptors, and the physiological role of thrombin in vascular cells and vascular disease.
Animals↗
Thrombin regulates vascular smooth muscle cell growth and heat shock proteins via the JAK-STAT pathway.
The growth-stimulating effects of thrombin are mediated primarily via activation of a G protein-coupled receptor, PAR-1. Because PAR-1 has no intrinsic tyrosine kinase activity, yet requires tyrosine phosphorylation events to induce mitogenesis, we investigated the role of the Janus tyrosine kinases (JAKs) in thrombin-mediated signaling. JAK2 was activated rapidly in rat vascular smooth muscle cells (VSMC) treated with thrombin, and signal transducers and activators of transcription (STAT1 and STAT3) were phosphorylated and translocated to the nucleus in a JAK2-dependent manner. AG-490, a JAK2-specific inhibitor, and a dominant negative JAK2 mutant inhibited thrombin-induced ERK2 activity and VSMC proliferation suggesting that JAK2 is upstream of the Ras/Raf/MEK/ERK pathway. To elucidate the functional significance of JAK-STAT activation, we studied the effect of thrombin on heat shock protein (Hsp) expression, based upon the following: 1) reports that thrombin stimulates reactive oxygen species production in VSMC; 2) the putative role of Hsps in modulating cellular responses to reactive oxygen species; and 3) the presence of functional STAT1/3-binding sites in Hsp70 and Hsp90beta promoters. Indeed, thrombin up-regulated Hsp70 and Hsp90 protein expression via enhanced binding of STATs to cognate binding sites in the Hsp70 and Hsp90 promoters. Together, these results suggest that JAK-STAT pathway activation is necessary for thrombin-induced VSMC growth and Hsp gene expression.
Animals↗
4-hydroxynonenal induces apoptosis, NF-kappaB-activation and formation of 8-isoprostane in vascular smooth muscle cells.
Oxidation of lipids is considered a key feature of atherogenesis. Lipid peroxidation products such as oxidized LDL or the bioactive aldehyde 4-hydroxynonenal (HNE) exert mitogenic effects on vascular smooth muscle cells (VSMC). These effects appear to be concentration-dependent since in addition to our previous reports on growth promotion at lower concentrations we here indicate induction of apoptosis in VSMC by 4-hydroxynonenal (HNE) at higher concentrations (100 micromol/L). In a line with HNE's previously documented effects on key mitogenic signaling elements, we also report on activation by this aldehyde of the redox-sensitive transcription factor NF-kappaB, a key regulator of apoptosis: HNE (1.0 micromol/L) induced DNA-binding of NF-kappaB in VSMC. The effect was inhibited by antioxidants, N-acetylcysteine and pyrrolidine dithio-carbamate. HNE caused phosphorylation but not degradation of the inhibitory subunit IkappaB-alpha. HNE itself acts as an oxidant as was investigated with measurements of 8-isoprostane which ranks among the most valuable available biomarkers of lipid peroxidation: HNE (1.0 micromol/L) increased 8-isoprostane levels in VSMC by 4.5-fold (p < 0.05). Compared to the controls, plasma samples from apoEnull mice exhibited elevated levels of 8-isoprostane (40 pg/mL, 3.2-fold increase) and the combined aldehydes HNE and malonaldehyde (1.5 micromol/L, 2.5-fold increase), (p < 0.05, resp). In addition, immunohistochemistry indicated the presence of HNE-protein adducts in atheroscerlotic lesions of apoEnull mice. Thus HNE is present in atherosclerotic tissue at concentrations that are bioactive in vitro. The data further indicate the involvement of the lipid peroxidation product HNE in atherogenesis.
Aldehydes↗
Shear stress reduces protease activated receptor-1 expression in human endothelial cells.
Shear stress has been shown to regulate several genes involved in the thrombotic and proliferative functions of endothelial cells. Thrombin receptor (protease-activated receptor-1: PAR-1) increases at sites of vascular injury, which suggests an important role for PAR-1 in vascular diseases. However, the effect of shear stress on PAR-1 expression has not been previously studied. This work investigates effects of shear stress on PAR-1 gene expression in both human umbilical vein endothelial cells (HUVECs) and microvascular endothelial cells (HMECs). Cells were exposed to different shear stresses using a parallel plate flow system. Northern blot and flow cytometry analysis showed that shear stress down-regulated PAR-1 messenger RNA (mRNA) and protein levels in both HUVECs and HMECs but with different thresholds. Furthermore, shear-reduced PAR-1 mRNA was due to a decrease of transcription rate, not increased mRNA degradation. Postshear stress release of endothelin-1 in response to thrombin was reduced in HUVECs and HMECs. Moreover, inhibitors of potential signaling pathways applied during shear stress indicated mediation of the shear-decreased PAR-1 expression by protein kinases. In conclusion, shear stress exposure reduces PAR-1 gene expression in HMECs and HUVECs through a mechanism dependent in part on protein kinases, leading to altered endothelial cell functional responses to thrombin.
Biomedical Engineering↗
Aging, oxidative responses, and proliferative capacity in cultured mouse aortic smooth muscle cells.
The cellular mechanisms that contribute to the acceleration of atherosclerosis in aging populations are poorly understood, although it is hypothesized that changes in the proliferative capacity of vascular smooth muscle cells is contributory. We addressed the relationship among aging, generation of reactive oxygen species (ROS), and proliferation in primary culture smooth muscle cells (SMC) derived from the aortas of young (4 mo old) and aged (16 mo old) mice to understand the phenotypic modulation of these cells as aging occurs. SMC from aged mice had decreased proliferative capacity in response to alpha-thrombin stimulation, yet generated higher levels of ROS and had constitutively increased mitogen-activated protein kinase activity, in comparison with cells from younger mice. These effects may be explained by dysregulation of cell cycle-associated proteins such as cyclin D1 and p27Kip1 in SMC from aged mice. Increased ROS generation was associated with decreased endogenous antioxidant activity, increased lipid peroxidation, and mitochondrial DNA damage. Accrual of oxidant-induced damage and decreased proliferative capacity in SMC may explain, in part, the age-associated transition to plaque instability in humans with atherosclerosis.
Aging↗
PTP-epsilon, a tyrosine phosphatase expressed in endothelium, negatively regulates endothelial cell proliferation.
The vascular endothelium is a dynamic interface between the blood vessel and circulating factors and, as such, plays a critical role in vascular events like inflammation, angiogenesis, and hemostasis. Whereas specific protein tyrosine kinases have been identified in these processes, less is known about their protein tyrosine phosphatase (PTP) counterparts. We utilized a RT-PCR/differential hybridization assay to identify PTP-epsilon as a highly abundant endothelial cell PTP. PTP-epsilon mRNA expression is growth factor responsive, suggesting a role for this enzyme in endothelial cell proliferation. Overexpression of PTP-epsilon decreases proliferation by 60% in human umbilical vein endothelial cells (HUVEC) but not in smooth muscle cells or fibroblasts. In contrast, overexpression of PTP-epsilon (D284A), a catalytically inactive mutant, has no significant effect on HUVEC proliferation. These data provide the first functional characterization of PTP-epsilon in endothelial cells and identify a novel pathway that negatively regulates endothelial cell growth. Such a pathway may have important implications in vascular development and angiogenesis.
Blood Physiological Phenomena↗
Reactive oxygen species regulate heat-shock protein 70 via the JAK/STAT pathway.
Reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) activate intracellular signal transduction pathways implicated in the pathogenesis of cardiovascular disease. H(2)O(2) is a mitogen for rat vascular smooth muscle cells (VSMCs), and protein tyrosine phosphorylation is a critical event in VSMC mitogenesis. Therefore, we investigated whether the mitogenic effects of H(2)O(2), such as stimulation of extracellular signal-regulated kinase (ERK)2, are mediated via activation of cytoplasmic Janus tyrosine kinases (JAKs). JAK2 was activated rapidly in VSMCs treated with H(2)O(2), and signal transducers and activators of transcription (STAT) STAT1 and STAT3 were tyrosine-phosphorylated and translocated to the nucleus in a JAK2-dependent manner. Inhibition of JAK2 activity with AG-490 partially inhibited H(2)O(2)-induced ERK2 activity, suggesting that JAK2 is upstream of the Ras/Raf/mitogen-activated protein kinase-ERK/ERK mitogenic pathway. Because heat-shock proteins (HSPs) can protect cells from ROS, we investigated the effect of H(2)O(2) on HSP expression. H(2)O(2) stimulated HSP70 expression in a time-dependent manner, and AG-490 abolished H(2)O(2)-induced HSP70 expression. H(2)O(2) activated the HSP70 promoter via enhanced binding of STATs to cognate binding sites in the promoter. Regulation of chaperones such as HSP70 via activation of the JAK/STAT pathway suggests that in addition to its growth-promoting effects, this pathway may help VSMCs adapt to oxidative stress.
Animals↗
Role of reactive oxygen species in angiotensin ii signaling : the plot thickens.
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Angiotensin II↗
The oxidative paradox: another piece in the puzzle.
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Antioxidants↗
Therapeutic myocardial angiogenesis via vascular endothelial growth factor gene therapy: moving on down the road.
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Angiogenesis Inducing Agents↗
Hydrogen peroxide- and peroxynitrite-induced mitochondrial DNA damage and dysfunction in vascular endothelial and smooth muscle cells.
The mechanisms by which reactive species (RS) participate in the development of atherosclerosis remain incompletely understood. The present study was designed to test the hypothesis that RS produced in the vascular environment cause mitochondrial damage and dysfunction in vitro and, thus, may contribute to the initiating events of atherogenesis. DNA damage was assessed in vascular cells exposed to superoxide, hydrogen peroxide, nitric oxide, and peroxynitrite. In both vascular endothelial and smooth muscle cells, the mitochondrial DNA (mtDNA) was preferentially damaged relative to the transcriptionally inactive nuclear beta-globin gene. Similarly, a dose-dependent decrease in mtDNA-encoded mRNA transcripts was associated with RS treatment. Mitochondrial protein synthesis was also inhibited in a dose-dependent manner by ONOO(-), resulting in decreased cellular ATP levels and mitochondrial redox function. Overall, endothelial cells were more sensitive to RS-mediated damage than were smooth muscle cells. Together, these data link RS-mediated mtDNA damage, altered gene expression, and mitochondrial dysfunction in cell culture and reveal how RS may mediate vascular cell dysfunction in the setting of atherogenesis.
Cells, Cultured↗
Construction and functional evaluation of a single-chain antibody fusion protein with fibrin targeting and thrombin inhibition after activation by factor Xa.
BACKGROUND: Recombinant technology was used to produce a new anticoagulant that is preferentially localized and active at the site of the clot. METHODS AND RESULTS: The variable regions of the heavy and light chains of a fibrin-specific antibody were amplified by polymerase chain reaction (PCR) with hybridoma cDNA. To obtain a functional single-chain antibody (scFv), a linker region consisting of (Gly(4)Ser)(3) was introduced by overlap PCR. After the scFv clones were ligated with DNA encoding the pIII protein of the M13 phage, high-affinity clones were selected by 10 rounds of panning on the Bbeta15-22 peptide of fibrin (beta-peptide). Hirudin was genetically fused to the C-terminus of the variable region of the light chain. To release the functionally essential N-terminus of hirudin at the site of a blood clot, a factor Xa recognition site was introduced between scFv(59D8) and hirudin. The fusion protein was characterized by its size on SDS-PAGE (36 kDa), by Western blotting, by its cleavage into a 29-kDa (single chain alone) and 7-kDa (hirudin) fragment, by its binding to beta-peptide, and by thrombin inhibition after Xa cleavage. Finally, the fusion protein inhibited appositional growth of whole blood clots in vitro more efficiently than native hirudin. CONCLUSIONS: A fusion protein was constructed that binds to a fibrin-specific epitope and inhibits thrombin after its activation by factor Xa. This recombinant anticoagulant effectively inhibits appositional clot growth in vitro. Its efficient and fast production at low cost should facilitate a large-scale evaluation to determine whether an effective localized antithrombin activity can be achieved without systemic bleeding complications.
Amino Acid Sequence↗
High-output heart failure resulting from a remote traumatic aorto-caval fistula: diagnosis by echocardiography.
Congestive heart failure (CHF) due to high output states is known to occur in a variety of systemic illnesses and in patients with arterial-venous fistulas. This paper reports the case of a 45-year-old man admitted to the emergency room with a diagnosis of new onset atrial fibrillation and CHF, whose past medical history was not significant except for a gunshot wound to his abdomen 22 years previously. The etiology of his CHF together with the cardiomegaly and hyperdynamic left ventricular systolic function was unknown. A subcostal view routinely done during transthoracic echocardiography revealed a severely dilated inferior vena cava and the presence of an aorto-caval fistula by color doppler. The patient underwent successful corrective repair with dramatic improvement in symptoms and resolution of the atrial fibrillation, and cardiac size returned to normal. This rare case emphasizes that patients with refractory CHF must be closely examined with particular attention to palpation and auscultation over all scars, irrespective of the duration since any traumatic or surgical event.
Abdominal Injuries↗
Indications for the presence of an atypical protease-activated receptor on rat platelets.
Activation of the protease-activated receptor (PAR)-1, one of four known PARs (PAR-1 to PAR-4), can be mimicked by thrombin receptor activating peptides (TRAPs) based on the PAR-1 tethered ligand. Interestingly, despite being activatable by thrombin, rodent platelets do not express PAR-1 and thus do not respond to PAR-1-derived TRAPs, indicating different activation mechanisms between human and rodent platelets. Using a rat platelet aggregation model, we determined that TRAPs based on the tethered ligand of PAR-1 fail to activate rat platelet aggregation at concentrations up to 1 mmol/l. In addition, TRAPs inhibit thrombin-mediated rat platelet aggregation, indicating the presence of a modified PAR-1 in this species. In order to determine characteristics of this putative receptor, we tested a panel of synthesized TRAPs based on the rat sequence (R) and human sequence (H) of the PAR-1 tethered ligand for their ability to inhibit thrombin-induced rat platelet aggregation. Peptides R1-9, R4-9, R4-10, and H4-10 inhibited rat platelet aggregation in response to alpha-thrombin [inhibitory concentration (IC) 50% 0.25-1.5 mmol/l]. None of these peptides blocked epinephrine-, collagen-, or arachidonic acid-induced platelet aggregation. Alanine substitution mapping of H4-10 indicated that both Leu4 and Arg5 are essential for inhibition. Inhibition of thrombin's catalytic activity required peptide concentrations tenfold higher than inhibition of platelet aggregation (IC50% 3-5 mmol/l). No prolongation of thrombin clotting time in response to TRAPs was detected at peptide concentrations up to 5 mmol/l. Our data suggest that (1) rat platelets express a PAR-1 subtype, (2) residues Leu4 and Arg5 of the tethered ligand peptide are required for binding to this new receptor, and (3) further analysis of peptide sequences might reveal a novel PAR-1 subtype.
Animals↗
Cardiac troponin T in chest pain unit patients without ischemic electrocardiographic changes: angiographic correlates and long-term clinical outcomes.
OBJECTIVES: We prospectively evaluated the relation between cardiac troponin T (cTnT) level, the presence and severity of coronary artery disease (CAD) and long-term prognosis in patients with chest pain but no ischemic electrocardiographic (ECG) changes who had short-term observation. BACKGROUND: Cardiac TnT is a powerful predictor of future myocardial infarction (MI) and death in patients with ECG evidence of an acute coronary syndrome. However, for patients with chest pain with normal ECGs, it has not been determined whether cTnT elevation is predictive of CAD and a poor long-term prognosis. METHODS: In 414 consecutive patients with no ischemic ECG changes who were triaged to a chest pain unit, cTnT and creatine kinase, MB fraction (CK-MB) were evaluated > or = 10 h after symptom onset. Patients with adverse cardiac events, including death, MI, unstable angina and heart failure were followed for as long as one year. RESULTS: A positive (>0.1 ng/ml) cTnT test was detected in 37 patients (8.9%). Coronary artery disease was found in 90% of 30 cTnT-positive patients versus 23% of 144 cTnT-negative patients who underwent angiography (p < 0.001), with multivessel disease in 63% versus 13% (p < 0.001). The cTnT-positive patients had a significantly (p < 0.05) higher percent diameter stenosis and a greater frequency of calcified, complex and occlusive lesions. Follow-up was available in 405 patients (98%). By one year, 59 patients (14.6%) had adverse cardiac events. The cumulative adverse event rate was 32.4% in cTnT-positive patients versus 12.8% in cTnT-negative patients (p = 0.001). After adjustment for baseline clinical characteristics, positive cTnT was a stronger predictor of events (chi-square = 23.56, p = 0.0003) than positive CK-MB (>5 ng/ml) (chi-square = 21.08, p = 0.0008). In a model including both biochemical markers, CK-MB added no predictive information as compared with cTnT alone (chi-square = 23.57, p = 0.0006). CONCLUSIONS: In a group of patients with chest pain anticipated to have a low prevalence of CAD and a good prognosis, cTnT identifies a subgroup with a high prevalence of extensive and complex CAD and increased risk for long-term adverse outcomes.
Cardiology Service, Hospital↗
Morphological patterns of death by myocytes in arrhythmogenic right ventricular dysplasia.
There are two forms of nuclear loss from eukaryotic cells: biochemical DNA degradation in apoptosis and nuclear extrusion from the cell body as seen in mammalian erythroblasts. In biopsies of right ventricular myocardium from 8 patients with arrhythmogenic right ventricular dysplasia (ARVD), we found not only a terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine triphosphate nick-end labeling (TUNEL)-positive nucleus in mononuclear myocytes, but also 1 or 2 TUNEL-positive nuclei in multinuclear myocytes. With electron microscopy, we found a nuclear dislocation to the cell periphery, followed by its extrusion into the extracellular space. Both the migration and extrusion of the nuclei of myocytes resemble the morphogenesis of human erythroblasts. Nuclear extrusion from myocytes may be another form of programmed cell death. In support of this possibility, we also found evidence of cytoplasmic degradation in right ventricular myocytes from our ARVD cases, a process similar to one often seen in developmental programmed cell death and differing from typical nuclear apoptosis. In our ARVD cases, we thus found several different patterns of cell death, all associated with initial preservation of the plasmalemma and avoidance of local inflammation. All these features may be different responses to common signals for selective non-necrotic (apoptotic) death of right ventricular myocytes.
Adult↗