Norepinephrine stimulates apoptosis in adult rat ventricular myocytes by activation of the beta-adrenergic pathway

BACKGROUND: Myocardial sympathetic activity is increased in heart failure. We tested the hypothesis that norepinephrine (NE) stimulates apoptosis in adult rat ventricular myocytes in vitro. METHODS AND RESULTS: Myocytes were exposed to NE alone (10 micromol/L), NE+propranolol (2 micromol/L), NE+prazosin (0.1 micromol/L), or isoproterenol (ISO, 10 micromol/L) for 24 hours. NE and ISO decreased the number of viable myocytes by approximately 35%. This effect was completely blocked by the beta-adrenergic antagonist propranolol but was not affected by the alpha1-adrenergic antagonist prazosin. NE increased DNA laddering on agarose gel electrophoresis and increased the percentage of cells that were stained by terminal deoxynucleotidyl transferase-mediated nick end-labeling from 5.8+/-1. 0% to 21.0+/-2.3% (P<0.01; n=4). NE likewise increased the percentage of apoptotic cells with hypodiploid DNA content as assessed by flow cytometry from 7.8+/-0.7% to 16.7+/-2.2% (P<0.01; n=6), and this effect was abolished by propranolol but not prazosin. ISO and forskolin (10 micromol/L) mimicked the effect of NE, increasing the percentage of apoptotic cells to 14.7+/-1.9% and 14. 4+/-2.2%, respectively. NE-stimulated apoptosis was abolished by the protein kinase A inhibitor H-89 (20 micromol/L) or the voltage-dependent calcium channel blockers diltiazem and nifedipine. CONCLUSIONS: NE, acting via the ss-adrenergic pathway, stimulates apoptosis in adult rat cardiac myocytes in vitro. This effect is mediated by protein kinase A and requires calcium entry via voltage-dependent calcium channels. NE-stimulated apoptosis of cardiac myocytes may contribute to the progression of myocardial failure.     

Reversible phosphorylation of Bcl2 following interleukin 3 or bryostatin 1 is mediated by direct interaction with protein phosphatase 2A

Interleukin 3 (IL-3) stimulates the net growth of murine factor-dependent NSF/N1.H7 and FDC-P1/ER myeloid cells by stimulating proliferation and suppressing apoptosis. Recently, we discovered that Bcl2 is phosphorylated at an evolutionarily conserved serine residue (Ser70) after treatment with the survival agonists IL-3 or bryostatin 1, a potent activator of protein kinase (Ito, T., Deng, X., Carr, B., and May, W. S. (1997) J. Biol. Chem. 272, 11671-11673). In addition, an intact Ser70 was found to be required for Bcl2's ability to suppress apoptosis after IL-3 withdrawal or toxic chemotherapy. We now show that phosphorylation of Bcl2 occurs rapidly after the addition of agonist to IL-3-deprived cells and can be reversed by the action of an okadaic acid (OA)-sensitive phosphatase. A role for protein phosphatase (PP) 2A as the Bcl2 regulatory phosphatase is supported by several observations: 1) dephosphorylation of Bcl2 is blocked by OA, a potent PP1 and PP2A inhibitor; 2) intracellular PP2A, but not PP1, co-localizes with Bcl2; 3) the purified PP2Ac catalytic subunit directly dephosphorylates Bcl2 in vitro in an OA-sensitive manner; 4) the purified PP2Ac catalytic subunit preferentially dephosphorylates Bcl2 in vitro compared with PP1 and PP2B; 5) reciprocal immunoprecipitation studies indicate a direct interaction between PP2A and hemagglutinin (HA)-Bcl2; and 6) treatment of factor-deprived cells with bryostatin 1 dramatically increases the association between PP2A and Bcl2. Increased association between Bcl2 and PP2A occurs 15 min after agonist stimulation when Bcl2 phosphorylation has peaked and immediately before dephosphorylation. An agonist-induced increased association of PP2A and Bcl2 fails to occur in cells expressing the inactive, phosphorylation-negative S70A Bcl2 mutant, which indicates that an intact Ser70 site is necessary and sufficient for the interaction to occur. Functional phosphorylation of Bcl2 at Ser70 is proposed to be a dynamic process regulated by the sequential action of an agonist-activated Bcl2 kinase and PP2A.     

A study on the cost-effectiveness of coronary revascularization: introducing the simultaneous mimic health status model

An econometric model is presented to compare the cost-effectiveness of two alternative procedures, percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass surgery (CABG), for the treatment of multivessel coronary artery disease. This study utilizes the MIMIC (multiple indicator multiple cause) health model in a simultaneous equation system to analyse Emory Angioplasty Surgery Trial (EAST) data. This method eliminates the possibility of endogeneity bias, which may have affected the results of previous cost-effectiveness analyses on this topic. The empirical results indicate that neither procedure proves more cost-effective at 3 year follow-up.     

Human autoantibodies recognizing a native macromolecular structure composed of Sm core proteins in U small nuclear RNP particles

OBJECTIVE: Monoclonal antibody (mAb) F78 recognizes a heat-labile particle composed of Sm core proteins designated F78P. The objective of this study was to identify human autoantibodies recognizing the conformational structure of F78P. METHODS: Immunoblots using HeLa cell extracts without heating prior to sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used to identify autoantibodies recognizing F78P. To confirm reactivities with F78P, immunoprecipitates of mAb F78 were used as a substrate for immunoblots. To identify reactivities against the F78P structure in classic anti-Sm-positive sera, autoantibodies to individual Sm core proteins were absorbed with purified U1 small nuclear RNP before immunoblotting. RESULTS: We identified 2 sera that, like F78, recognized only F78P and not its component polypeptides. When classic anti-Sm antibodies were preabsorbed, the presence of F78-like, particle-specific antibodies was revealed in all of the anti-Sm-positive sera tested. CONCLUSION: Autoantibodies against the F78P structure were commonly present in sera from patients with systemic rheumatic diseases, often in combination with4=1998 M autoantibodies.     

Signal-averaged electrocardiography in elderly subjects with and without heart disease

Despite a high level of support for the importance of clinical prevention, physician delivery of preventive services falls well below recommended levels. Competing demands faced by physicians during the medical encounter present a major barrier to the provision of specific preventive services to patients. These demands include acute care, patient requests, chronic illnesses, psychosocial problems, screening for asymptomatic disease, counseling for behavior change, other preventive services, and administration and management of care. This paper outlines how competing demands affect physician delivery of clinical preventive services and provides a model designed to help practicing physicians improve the delivery of preventive services. This model can be helpful in the planning of preventive interventions in primary care settings and can facilitate a better understanding of physician behavior.     

Use of high-precision gas isotope ratio mass spectrometry to determine natural abundance 13C in lutein isolated from C3 and C4 plant sources

Previous studies have shown that cholesterol esterification activity by lecithin:cholesterol acyltransferase (LCAT) is progressively inhibited as up to three acidic acid residues are chemically modified. The purpose of this study was to determine whether three glutamic acid residues in LCAT (154, 155, and 165), that align exactly with three acidic acid residues (270, 271, and 281) in the amphipathic phospholipid binding region of apoE, were necessary for enzymatic activity. Site-directed mutagenesis was used to generate mutant constructs of LCAT in which glutamic acid residues 154, 155, and 165 were replaced with glutamine or lysine. Media harvested from transiently transfected COS cells was used as a source of LCAT for cholesterol esterification and phospholipase A2 (PLA2) assays. Cholesterol esterification for all mutant constructs (11-26 nmol CE/h/microg) was similar to or greater than that of wild type LCAT (16 nmol CE/h/microg), except for a triple mutant, in which glutamic acid residues 154, 155, and 165 were changed to lysines (5 nmol CE/h/microg). PLA2 activity followed a similar trend. There was a significant decrease in the cholesterol esterification to PLA2 activity ratio when residue 165 was mutated from its wild type negative charge (E) to an uncharged (Q) or positive (K) charged residue (10.2 vs. 6.0 vs. 4.3, respectively). We conclude that glutamic acid residues 154, 155, and 165 individually or collectively are not necessary for LCAT activity and that residue 165 may be in a region of LCAT that is involved with cholesterol binding or is sensitive to cholesterol binding at the active site of the enzyme.     

Metabolism of 5(S)-hydroxyeicosanoids by a specific dehydrogenase in human neutrophils

We have previously shown that human polymorphonuclear leukocytes (PMNL) convert 6-trans isomers of leukotriene B4 (LTB4) to 6,11-dihydro metabolites (Powell and Gravelle (1988) J. Biol. Chem. 263, 2170-2177). In the present study, we have shown that the first step in the formation of these dihydro metabolites is oxidation of the 5-hydroxyl group to a 5-oxo group, which is catalyzed by an NADP(+)-dependent microsomal dehydrogenase enzyme. All the dihydroxyeicosanoids we investigated which contained a 5(S)-hydroxyl group followed by a 6-trans double bond were good substrates for this reaction. However, LTB4, which contains a 6-cis double bond, was not metabolized to any detectable 5-oxo products. The preferred substrate for the dehydrogenase reaction is 5(S)-hydroxy-6,8,11,14-eicosatetraenoic acid (5(S)-HETE), which has a Km of about 0.2 microM, compared to approx. 0.9 microM for 12-epi-6-trans-LTB4. In contrast to 5(S)-HETE, 5(R)-HETE as well as a variety of positional isomers of 5(S)-HETE are not metabolized to significant extents by the PMNL dehydrogenase. 5-Oxo-ETE and 5-oxo-15-hydroxy-ETE, which are formed from 5(S)-HETE and 5,15-diHETE, respectively, by this pathway, are potent chemotactic agents for human neutrophils, and raise intracellular calcium levels in these cells.     

Locoregional response and increased natural killer activity after intratumoral injection of HLA-B7/beta2-microglobulin gene in patients with cancer

The purpose of this study was to assess the therapeutic potential of injecting the gene for HLA-B7/beta2-microglobulin into the subcutaneous metastatic nodules of patients who are refractory to conventional treatments. The nine patients evaluated were divided into three groups and given escalating doses of DNA (20, 40, and 100 microg of the HLA-B7 plasmid DNA/lipid complex for each group) every 2 weeks. Biopsy specimens from the treated tumor nodules of all nine patients were positive for the presence of DNA and for HLA-B7 mRNA expression. Moreover, in six of the nine patients, immunohistology of tumor biopsy samples revealed the expression of recombinant HLA-B7 protein. Also, all nine patients showed an increase in NK activity in their circulating peripheral blood lymphocytes. In two lung cancer patients, one partial and one mixed response was observed after gene transfer. These responses were confined to the treated nodules and the untreated locoregional lymph nodes; the lung masses showed no regression. Remission durations were 14 and 6 weeks, respectively, and in a total of 35 cycles no significant toxicities were observed. Immunohistologic analysis revealed an increased infiltration of CD4+ T cells, macrophages, and NK cells after therapy. In two responding cases, direct intratumoral injection of an allogeneic class I gene could elicit an antitumor response in locoregional areas, possibly through the activation of NK cells.