AMP-activated protein kinase phosphorylation of endothelial NO synthase.
The AMP-activated protein kinase (AMPK) in rat skeletal and cardiac muscle is activated by vigorous exercise and ischaemic stress. Under these conditions AMPK phosphorylates and inhibits acetyl-coenzyme A carboxylase causing increased oxidation of fatty acids. Here we show that AMPK co-immunoprecipitates with cardiac endothelial NO synthase (eNOS) and phosphorylates Ser-1177 in the presence of Ca2+-calmodulin (CaM) to activate eNOS both in vitro and during ischaemia in rat hearts. In the absence of Ca2+-calmodulin, AMPK also phosphorylates eNOS at Thr-495 in the CaM-binding sequence, resulting in inhibition of eNOS activity but Thr-495 phosphorylation is unchanged during ischaemia. Phosphorylation of eNOS by the AMPK in endothelial cells and myocytes provides a further regulatory link between metabolic stress and cardiovascular function. (+info
Differential regulation of Bcl-2, AP-1 and NF-kappaB on cardiomyocyte apoptosis during myocardial ischemic stress adaptation.
Acute ischemia followed by prolonged reperfusion has been shown to induce cardiomyocyte apoptosis. In this report, we demonstrate that myocardial adaptation to ischemia induced by repeated cyclic episodes of short-term ischemia each followed by another short duration of reperfusion reduced cardiomyocyte apoptosis and DNA fragmentation. This was associated with the induction of the expression of Bcl-2 mRNA and translocation and activation of NF-kappaB. Another transcription factor, AP-1, remained unaffected by repeated ischemia and reperfusion, but exhibited significant upregulation by a single episode of 30 min ischemia followed by 2 h of reperfusion. This activation of AP-1 was inhibited by a scavenger of oxygen free radicals, DMTU. Thirty minutes ischemia and 120 min reperfusion downregulated the induction of the expression of Bcl-2 mRNA, but moderately activated NF-kappaB binding activity. This was associated with an increased number of apoptotic cells and DNA fragmentation in cardiomyocytes which were attenuated by DMTU. The results of this study indicate that Bcl-2, AP-1 and NF-kappaB differentially regulate cardiomyocyte apoptosis mediated by acute ischemia and prolonged reperfusion. (+info
Chlamydia pneumoniae antibodies are associated with an atherogenic lipid profile.
OBJECTIVE: To determine, within a representative population group of men and women, whether alteration of the lipid profile might underlie the reported association between Chlamydia pneumoniae and ischaemic heart disease. DESIGN AND SETTING: Cross sectional survey in an area with a high incidence of ischaemic heart disease. SUBJECTS: 400 randomly selected participants in the World Health Organisation MONICA project's third population survey in Northern Ireland. MAIN OUTCOME MEASURES: Stored sera were examined by microimmunofluorescence for IgG antibodies to C pneumoniae at a dilution of 1 in 64. Mean total and high density lipoprotein (HDL) cholesterol were compared between seropositive and seronegative individuals with adjustment for age, measures of socioeconomic status, smoking habit, alcohol consumption, body mass index, and the season during which blood had been taken. RESULTS: In seropositive men, adjusted mean serum total cholesterol and HDL cholesterol were 0.5 mmol/l (9.2%) higher and 0.11 mmol/l (9.3%) lower, respectively, than in seronegative men. Differences in women did not achieve statistical significance, but both total cholesterol and HDL cholesterol were higher (3.6% and 5.8%, respectively) in seropositive than in seronegative individuals. CONCLUSIONS: There is serological evidence that C pneumoniae infection is associated with an atherogenic lipid profile in men. Altered lipid levels may underlie the association between C pneumoniae and ischaemic heart disease. (+info
Cytomegalovirus seropositivity and incident ischaemic heart disease in the Caerphilly prospective heart disease study.
OBJECTIVE: To assess the role of cytomegalovirus (CMV) infection in primary ischaemic heart disease. METHODS: Plasma specimens collected during 1979-83 from men in Caerphilly, south Wales, were analysed for IgG antibodies to CMV by enzyme linked immunosorbent assay and latex tests. Incident ischaemic heart disease events were ascertained after five and 10 years from death certificates, hospital records, and ECG changes; 195 incident ischaemic heart disease cases were compared with 216 controls of a similar age drawn from the rest of the cohort. RESULTS: 164 cases (84%) and 180 controls (83%) were seropositive for CMV. Optical density, an indicator of CMV antibody titre, was similar for cases and controls. Among controls, seropositivity was not associated with age, socioeconomic status currently or in childhood, smoking, height, body mass index, blood pressure, total cholesterol, fibrinogen, plasma viscosity, or leucocyte count. The unadjusted odds ratio relating CMV seropositivity to incident ischaemic heart disease was 1.06 (95% confidence interval 0.63 to 1.79) and was little changed (1.11, 0.63 to 1.97) after adjustment for age, smoking, body mass index, systolic blood pressure, total cholesterol, and socioeconomic status currently and in childhood. CONCLUSIONS: CMV infection is unlikely to be a strong risk factor for development of myocardial infarction in middle aged men. (+info
Reactive oxygen species play an important role in the activation of heat shock factor 1 in ischemic-reperfused heart.
BACKGROUND: The myocardial protective role of heat shock protein (HSP) has been demonstrated. Recently, we reported that ischemia/reperfusion induced a significant activation of heat shock factor (HSF) 1 and an accumulation of mRNA for HSP70 and HSP90. We examined the role of reactive oxygen species (ROSs) in the induction of stress response in the ischemic-reperfused heart. METHODS AND RESULTS: Rat hearts were isolated and perfused with Krebs-Henseleit buffer by the Langendorff method. Whole-cell extracts were prepared for gel mobility shift assay using oligonucleotides containing the heat shock element. Induction of mRNA for HSP70 and HSP90 was examined by Northern blot analysis. Repetitive ischemia/reperfusion, which causes recurrent bursts of free radical generation, resulted in burst activation of HSF1, and this burst activation was significantly reduced with either allopurinol 1 mmol/L (an inhibitor of xanthine oxidase) or catalase 2x10(5) U/L (a scavenger of H2O2). Significant activation of HSF1 was observed on perfusion with buffer containing H2O2 150 micromol/L or xanthine 1 mmol/L plus xanthine oxidase 5 U/L. The accumulation of mRNA for HSP70 or HSP90 after repetitive ischemia/reperfusion was reduced with either allopurinol or catalase. CONCLUSIONS: Our findings demonstrate that ROSs play an important role in the activation of HSF1 and the accumulation of mRNA for HSP70 and HSP90 in the ischemic-reperfused heart. (+info
Bradykinin promotes ischemic norepinephrine release in guinea pig and human hearts.
We previously reported that bradykinin (BK; 1-1000 nM) facilitates norepinephrine (NE) release from cardiac sympathetic nerves. Because BK production increases in myocardial ischemia, endogenous BK could foster NE release and associated arrhythmias. We tested this hypothesis in guinea pig and human myocardial ischemia models. BK administration (100 nM) markedly enhanced exocytotic and carrier-mediated NE overflow from guinea pig hearts subjected to 10- and 20-min ischemia/reperfusion, respectively. Ventricular fibrillation invariably occurred after 20-min global ischemia; BK prolonged its duration 3-fold. The BK B2 receptor antagonist HOE140 (30 nM) blocked the effects of BK, whereas the B1 receptor antagonist des-Arg9-Leu8-BK (1 microM; i.e., 2.5 x pA2) did not. When serine proteinase inhibitors (500 KIU/ml aprotinin and 100 microg/ml soybean trypsin inhibitor) were used to prevent the formation of endogenous BK, NE overflow and reperfusion arrhythmias were diminished. In contrast, when kininase I and II inhibitors (DL-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid and enalaprilat, each 1 microM) were used to prevent the degradation of endogenous BK, NE overflow and reperfusion arrhythmias were enhanced. B2 receptor blockade abolished these effects but was ineffective if kininases were not inhibited. B2 receptor stimulation, by either exogenous or endogenous BK, also markedly enhanced carrier-mediated NE release in the human myocardial ischemia model; conversely, inhibition of BK biosynthesis diminished ischemic NE release. Because atherosclerotic heart disease impairs endothelial BK production, in myocardial ischemia BK could accumulate at sympathetic nerve endings, thus augmenting exocytotic and carrier-mediated NE release and favoring coronary vasoconstriction and arrhythmias. (+info
Labeling of the internal pool of GP IIb-IIIa in platelets by c7E3 Fab fragments (abciximab): flow and endocytic mechanisms contribute to the transport.
Abciximab is a new antiplatelet therapeutic in ischemic cardiovascular disease. The drug, chimeric Fab fragments of a murine monoclonal antibody (MoAb) (c7E3), blocks GP IIb-IIIa function. However, its capacity to reach all receptor pools in platelets is unknown. Electron microscopy and immunogold labeling were used to localize abciximab in platelets of patients receiving the drug for up to 24 hours. Studies on frozen-thin sections showed that c7E3 Fab, in addition to the surface pool, also labeled the surface-connected canalicular system (SCCS) and alpha-granules. Analysis of gold particle distribution showed that intraplatelet labeling was not accumulative and in equilibrium with the surface pool. After short-term incubations of platelets with c7E3 Fab in vitro, gold particles were often seen in lines within thin elements of the SCCS, some of which appeared in contact with alpha-granules. Little labeling was associated with Glanzmann's thrombasthenia platelets, confirming that the channels contained bound and not free c7E3 Fab. Endocytosis of abciximab in clathrin-containing vesicles was visualized by double staining and constitutes an alternative mechanism of transport. The remaining free pool of GP IIb-IIIa was evaluated with the MoAb AP-2; flow cytometry showed it to be about 9% on the surface of nonstimulated platelets but 33% on thrombin-activated platelets. The ability of drugs to block all pools of GP IIb-IIIa and then to be associated with secretion-dependent residual aggregation must be considered when evaluating their efficiency in a clinical context. (+info
An inhibitor of p38 mitogen-activated protein kinase protects neonatal cardiac myocytes from ischemia.
Cellular ischemia results in activation of a number of kinases, including p38 mitogen-activated protein kinase (MAPK); however, it is not yet clear whether p38 MAPK activation plays a role in cellular damage or is part of a protective response against ischemia. We have developed a model to study ischemia in cultured neonatal rat cardiac myocytes. In this model, two distinct phases of p38 MAPK activation were observed during ischemia. The first phase began within 10 min and lasted less than 1 h, and the second began after 2 h and lasted throughout the ischemic period. Similar to previous studies using in vivo models, the nonspecific activator of p38 MAPK and c-Jun NH2-terminal kinase, anisomycin, protected cardiac myocytes from ischemic injury, decreasing the release of cytosolic lactate dehydrogenase by approximately 25%. We demonstrated, however, that a selective inhibitor of p38 MAPK, SB 203580, also protected cardiac myocytes against extended ischemia in a dose-dependent manner. The protective effect was seen even when the inhibitor was present during only the second, sustained phase of p38 MAPK activation. We found that ischemia induced apoptosis in neonatal rat cardiac myocytes and that SB 203580 reduced activation of caspase-3, a key event in apoptosis. These results suggest that p38 MAPK induces apoptosis during ischemia in cardiac myocytes and that selective inhibition of p38 MAPK could be developed as a potential therapy for ischemic heart disease. (+info