Hiroshi Masuoka

Association of remnant-like particle cholesterol with coronary artery disease in patients with normal total cholesterol levels.

BACKGROUND Limited information is available as to whether there is a difference in the association of lipid and fibrinolytic variables with coronary artery disease according to the presence or absence of elevated serum total cholesterol. We examined the levels of various lipid and fibrinolytic variables including remnant-like particle cholesterol (RLP-C). RLP-C is a recently established simple assay method for the estimation of triglyceride-rich lipoprotein remnants. METHODS AND RESULTS Levels of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), triglyceride, lipoprotein(a), RLP-C, uric acid, blood glucose, tissue plasminogen activator, tissue plasminogen activator inhibitor type 1, antithrombin III, and protein C were measured in 208 patients who underwent diagnostic coronary angiograms. Of these 208 patients, 57 were hypercholesterolemic (> or =220 mg/dL) and 151 were normocholesterolemic. HDL-C showed significant differences between patients with and those without angiographically determined coronary artery stenosis in both hypercholesterolemic and normocholesterolemic patients (P =.0025 and P =.0003, respectively). Both RLP-C and uric acid showed significant differences only in the normocholesterolemic subgroup (P =.0006 and P =.0060, respectively). This difference in uric acid was not significant by multivariable analysis. The ratio of RLP-C/HDL-C was demonstrated to be highly significantly (P <.0001) associated with coronary artery stenosis in patients with normal total cholesterol, whereas there was no statistically significant association in the hypercholesterolemic patient subgroup. CONCLUSIONS Our current study disclosed that RLP-C levels are strongly associated with coronary artery disease, especially in patients with normal total cholesterol levels. Moreover, RLP-C/HDL-C ratio may be even more significantly associated with the presence of coronary artery stenosis in normocholesterolemic patients.

IDENTIFICATION AND CHARACTERIZATION OF ISOENZYMES OF CYCLIC NUCLEOTIDE PHOSPHODIESTERASE IN HUMAN KIDNEY AND HEART, AND THE EFFECTS OF NEW CARDIOTONIC AGENTS ON THESE ISOENZYMES

The present study was done to identify and characterize the isoenzymes of cyclic nucleotide phosphodiesterase (PDE) and to determine their intracellular distribution in human kidney and heart. The in vitro effects of new cardiotonic agents, namely, NSP-805 (4,5-dihydro-5-methyl-6-[4-[(2-methyl-3-oxo-1-cyclopentenyl)amino] phenyl]-3(2H)-pyridazinone), TZC-5665 (6-[4-[2-[3-(5-chloro-2-cyanophenoxy)-2-hydroxypropylamino]-2-methylpropylamino]phenyl]-5-methyl-4,5-dihydro-3(2 H)-pyridazinone) and its metabolites, OPC-18790 ((±)-6-[3-(3,4-dimethoxybenzylamino)-2-hydroxypropoxy]-2-(1H)-quinolinone), MS-857 (4-acetyl-l-methyl-7-(4-pyridyl)-5,6,7,8-tetrahydro-3(2H)-isoquinolinone) and E-1020 (1,2-dihydro-6-methyl-2-oxo-5-(imidazo[1,2-a]pyridin-6yl)-3-pyridine carbonitrile hydrochloride monohydrate), on these human PDE isoenzymes were also investigated.PDE isoenzymes were separated from cytosolic and particulate fractions of homogenates of human kidney and heart by DEAE-Sepharose chromatography. PDE isoenzymes were identified by their elution characteristics, substrate specificities, sensitivities to regulation by effectors and by the use of isoenzyme-specific inhibitors.In a cytosolic fraction from kidney, Ca2+/calmodulin-dependent PDE (CaM-PDE), cyclic GMP-stimulated PDE (cGS-PDE), cyclic GMP-inhibited PDE (cGI-PDE) and two forms of cyclic AMP-specific PDE (cAMP-PDE) were resolved. One form of cAMP-PDE (cAMP-PDEα), which was eluted at a lower ionic strength than cGI-PDE during DEAE-Sepharose chromatography, was newly recognized in human tissues, though the other form (cAMP-PDEβ), which eluted later than cGI-PDE, had been previously isolated. Both of these cAMP-specific PDEs had similar properties in that they predominantly hydrolyzed cAMP with similar Km values for cAMP and were inhibited to almost equal extents by 3-isobutyl-l-methylxanthine (IBMX) but were hardly inhibited by cGMP. However, cAMP-PDEα was inhibited about 10 times more weakly (on the basis of IC50 values) by rolipram (4-(3-cyclopentyloxy-4-methoxyphenyl)-2-pyrrolidone) and Ro 20-1724 (4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone than was cAMP-PDEβ. In a cytosolic fraction from heart ventricle, four distinct PDE isoenzymes, CaM-PDE, cGS-PDE, cGI-PDE and cAMP-PDEβ, were recognized. cAMP-PDEβ was the major component of the cAMP-hydrolyzing activity in the cytosolic fraction from human kidney, while CaM-PDE and cGI-PDE represented more than 90% of the total cAMP phosphodiesterase activity in the cytosolic fraction from human heart. In the particulate fractions from human kidney and heart, three activities, those of cGI-PDE and of two forms of cAMP-PDE, were identified. In kidney, cAMP/PDEα was the main cAMP-hydrolyzing PDE, while in heart cGI-PDE accounted for most of the activity. Furthermore, we evaluated the inhibitory effects on these human PDE isoenzymes of newly synthesized compounds with inotropic effects, namely, NSP-805, metabolites of TZC-5665 referred to as M-1 (6-(4-aminophenyl)-5-methyl-4,5-dihydro-3(2H)-pyridazinone) and M-2 (6-(4-acetyl-aminophenyl)-5-methyl-4,5-dihydro-3(2H)-pyridazinone), OPC-18790, MS-857 and E-1020. These drugs potently inhibited the activity of cGI-PDE and very weakly inhibited the activities of CaM-PDE and cGS-PDE. With respect to inhibitory effects on cardiac cAMP-PDEβ, there were some differences between the pyridazinone derivatives, for example NSP-805 and M-2, and the nonpyridazinone derivatives OPC-18790, MS-857 and E-1020. From the IC50 values, it was clear that the pyridazinone derivatives inhibited the activity of cGI-PDE at concentrations that were two to four orders of magnitude lower than that required for the inhibition of the activity of cAMP-PDEβ, while for the nonpyridazinone derivatives the difference was about one order of magnitude. The inhibition of the activity of human cardiac cGI-PDE by NSP-805, M2, OPC-18790, MS-857 and E-1020 was competitive with respect to cAMP with Ki values of 0.012, 0.32, 0.42, 1.3 and 0.15 μmol/l, respectively.These results suggest that there may be two isoforms of cAMP-PDE, which exist not only in the particulate fraction but also in the cytosolic fraction of human tissues, and that PDE inhibitors, which exert their cardiotonic effects by inhibiting cGI-PDE, have different selectivities with respect to the inhibition of the other human PDE isoenzymes.

Effects of amrinone and enoximone on the subclasses of cyclic AMP phosphodiesterase from human heart and kidney

We observed the intracellular localization of low-Km cyclic adenosine monophosphate (cAMP) phosphodiesterase (PDEIII) subclasses in human heart in comparison to that in human kidney by using comparable potencies of specific inhibitors. PDEIII was observed in not only soluble fraction but particulate fraction in human heart and kidney. Both soluble and particulate PDEIII from human heart selectively hydrolyzed cAMP with similar Km values of 0.36 and 0.40 μM, respectively. They were potently inhibited by amrinone, enoximone, and cyclic guanosine monophosphate (cGMP), but were weakly inhibited by rolipram with much the same IC50 values. Although several animals having soluble and particulate PDEIII possess two pharmacologically distinct subclasses of PDEIII, human heart has only one form, cGMP-sensitive PDEIII. In contrast to cardiac PDEIII, both soluble and particulate PDEIII from human kidney were not readily inhibited by amrinone, enoximone, and cGMP, but rather strongly inhibited by rolipram. Human kidney contains only cGMP-less sensitive form of PDEIII in soluble and particulate fractions. These results suggest that the intracellular distribution of PDEIII subclasses in human hearts are significantly different from those in the hearts of other animal species, and subclasses of PDEIII in humans hearts could not be distinguished by intracellular localization but by organ specificity.

Effects of ruthenium red on activation of Ca2(+)-dependent cyclic nucleotide phosphodiesterase.

Ruthenium red inhibited Ca2(+)-dependent phosphodiesterase (Ca2(+)-PDE) selectively with an IC50 value of 15 microM. Increasing calmodulin concentration in the presence of both 100 microM and 4000 microM Ca2+ completely reversed the inhibition of Ca2(+)-PDE activity by ruthenium red. Ruthenium red-induced inhibition of Ca2(+)-PDE activity was also overcome by increasing the concentration of Ca2+ in the presence of both 200 ng and 2000 ng calmodulin, in sharp contrast to fluphenazine-induced inhibition of Ca2(+)-PDE. These results indicate that ruthenium red has distinct inhibitory mechanism which differs from that of calmodulin antagonists previously reported.

A case of primary cardiac lymphoma located in the pericardial effusion

Primary cardiac lymphoma is a rare disorder with a poor prognosis. We present here a case of 77-year-old woman who was diagnosed as having cardiac lymphoma antemortem according to a cytologic examination of the pericardial effusion. Determination of the levels of serum-soluble interleukin-2 receptor and serum deoxythymidine kinase was useful for the diagnosis. Echocardiography, computed tomography, magnetic resonance imaging, and gallium scan revealed neither lymphadenopathy nor tumor in the heart, so she was diagnosed as having malignant lymphoma that probably originated from the pericardium. Systemic chemotherapy with CHOP (cyclophosphamide, farmorubicin, oncovin, and prednisolone) resulted in a complete resolution of the pericardial effusion. She has been in remission 48 months after discontinuation of the chemotherapy.

An autopsy case of intracranial hemorrhage during tissue plasminogen activator infusion

SummaryWe describe an autopsy case of severe intracranial hemorrhage which occurred during the infusion of tissue plasminogen activator (t-PA) for acute myocardial infarction. A 75-year-old man was admitted with substernal chest pain of 3-h duration and elctro-cardiographic changes consistent with an acute inferior myocardial infarction. Physical examination was unremarkable, except for an initial blood pressure reading of 160/96 mmHg. The patient received 3,000 IU intravenous heparin followed by a 2.4 × 106 IU bolus dose of tissue plasminogen activator (t-PA) (Alteplase). This was followed by a drip infusion of 21.6 × 106 IU of t-PA over 1 h (total dose 41 mg). Thirty minutes after the infusion of t-PA was initiated, the patient suddenly lost consciousness and began to have violent convulsions, followed by cardiac arrest. Autopsy revealed massive hemorrhage in the bilateral cerebrum and brain stem. To our knowledge, this is the first case of sudden death during t-PA infusion therapy.