Diltiazem Inhibits Coronary Spasm via Inhibition of Cav1.2Phosphorylation and Protein Kinase C Activation in a Mouse Model of Coronary Spastic Angina.

Calcium antagonists are used for coronary spastic angina (CSA) treatment. We previously identified a phospholipase C (PLC) -δ1 gene variant that results in enhanced PLC activity in patients with CSA and developed a CSA animal model by generating vascular smooth muscle cell-specific human variant PLC-δ1 overexpression (PLC-TG) mice. In this study, we investigated the molecular mechanism of CSA using the PLC-TG mice and the inhibitory effect of a calcium antagonist, diltiazem hydrochloride (DL).We treated the PLC-TG and wild-type (WT) mice with oral DL or trichlormethiazide (TM) (control) for 2 weeks. Ergometrine injection-induced coronary spasm was observed on the electrocardiogram in all 5 PLC-TG mice treated with TM, but only in 1 of 5 PLC-TG mice treated with DL. Voltage-dependent calcium channel (Cav1.2) phosphorylation and protein kinase C (PKC) activity were enhanced in the aortas of PLC-TG mice treated with TM. DL treatment significantly inhibited Cav1.2 phosphorylation and PKC activity. Although total Cav1.2 expression was similar between WT and PLC-TG mice treated with TM, DL treatment significantly increased its expression in PLC-TG mice. Furthermore, its expression remained high after DL discontinuation. DL and PKC inhibitor suppressed intracellular calcium response to acetylcholine in cultured rat aortic smooth muscle cells transfected with variant PLC-δ1.These results indicate that enhanced PLC activity causes coronary spasm, presumably via enhanced Cav1.2 phosphorylation and PKC activity, both of which were inhibited by DL. Enhanced total Cav1.2 expression after DL discontinuation and high PKC activity may be an important mechanism underlying the calcium antagonist withdrawal syndrome.

Coupling factor 6 enhances the spontaneous microaggregation of platelets by decreasing cytosolic cAMP irrespective of antiplatelet therapy.

The spontaneous microaggregation of platelets (SMAPs) is a marker for the prognosis of patients with cardiovascular diseases. Coupling factor 6 (CF6) binds to the plasma membrane ATP synthase and functions as a pro-atherogenic molecule in the cardiovascular system. However, the role of CF6 in SMAPs and stroke remains unknown. In 650 consecutive patients, including those with acute-onset stroke, and 20 control subjects, platelet-rich plasma (PRP) was obtained, and SMAP was measured using a laser light-scattering aggregometer. The cytosolic cyclic adenosine monophosphate (cAMP) concentration in platelets was measured using an enzyme-linked immunosorbent assay. CF6 increased SMAPs in patients and control subjects to a similar degree by binding to the α- and ß-subunits of ATP synthase and inducing intracellular acidosis. It was abolished by PRP pretreatment with antibodies against CF6, and the α- or ß-subunit of the plasma membrane ATP synthase, and the ATP synthase inhibitor efrapeptin. CF6 increased SMAPs in patient groups with and without antiplatelet therapy to a similar degree, and no difference was found among the subgroups taking aspirin, thienopyridine or cilostazol. The cytosolic cAMP concentration in platelets was decreased by CF6 in the presence of the direct adenylate cyclase activator forskolin. Pretreatment of PRP with the Gs activator cholera toxin blocked the decrease, whereas the Gi inactivator pertussis toxin and cilostazol had no influence. The CF6-induced acceleration of SMAPs was suppressed by cholera toxin but not by cilostazol or pertussis toxin. CF6 enhanced SMAPs by decreasing cytosolic cAMP. Because it was observed irrespective of antiplatelet agents, CF6 appears to be a novel target for antiplatelet therapy.

Estrogen attenuates coupling factor 6-induced salt-sensitive hypertension and cardiac systolic dysfunction in mice.

In male coupling factor 6 (CF6)-overexpressing transgenic (TG) mice, a high-salt diet induces hypertension and cardiac systolic dysfunction with excessive reactive oxygen species generation. However, the role of gender in CF6-mediated pathophysiology is unknown. We investigated the effects of ovariectomy and estrogen replacement on hypertension, cardiac dysfunction and Rac1 activity, which activates radical generation and the mineralocorticoid receptor, in female TG mice. Fifteen-week-old male and female TG and wild-type (WT) mice were fed a normal- or high-salt diet for 60 weeks. Systolic and diastolic blood pressures were higher in the TG mice fed a high-salt diet than in those fed a normal-salt diet at 20-60 weeks in males but only at 60 weeks in females. The blood pressure elevation under high-salt diet conditions was concomitant with a decrease in left ventricular fractional shortening. In the WT mice, neither blood pressure nor cardiac systolic function was influenced by a high-salt diet. In the female TG mice, bilateral ovariectomy induced hypertension with cardiac systolic dysfunction 8 weeks after the initiation of a high-salt diet. The ratios of Rac1 bound to guanosine triphosphate (Rac1-GTP) to total Rac1 in the heart and kidneys were increased in the ovariectomized TG mice, and estrogen replacement abolished the CF6-mediated pathophysiology induced under the high-salt diet conditions. The overexpression of CF6 induced salt-sensitive hypertension, complicated by systolic cardiac dysfunction, but its onset was delayed in females. Estrogen has an important role in the regulation of CF6-mediated pathophysiology, presumably via the downregulation of Rac1.

Matrix metalloprotein-9 activation under cell-to-cell interaction between endothelial cells and monocytes: possible role of hypoxia and tumor necrosis factor-α.

Matrix metalloproteinase (MMP)-9 plays an important role in cardiovascular events. However, the mechanisms underlying in vivo activation of MMP-9 are largely unknown. We investigated the secretion and activation of MMP-9 under a cell-to-cell interaction, and the effects of hypoxia and cytokine. Human umbilical vein endothelial cell (HUVEC) and THP-1 (human monocyte cell line) were cultured individually, or cocultured under normoxic and hypoxic conditions. In a coculture of HUVEC and THP-1, proMMP-9 secretion was increased twofold compared with individual culture of HUVEC and THP-1, whereas MMP-2 secretion was unchanged. The increase in proMMP-9 secretion was suppressed by antiadhesion molecule antibodies and mitogen-activated protein kinase inhibitors, PD98059 (MAPK/ERK kinase1 inhibitor) and SP600125 (Jun N-terminal kinase inhibitor). ProMMP-9 secretion was increased by tumor necrosis factor (TNF)-α at 50 ng/ml (P < 0.05) but was not activated under normoxic (20%) conditions. ProMMP-9 in coculture was activated under hypoxic (<1%) conditions, and was potentiated by TNF-α (both P < 0.05). To further investigate the mechanism of hypoxia-induced MMP-9 activation, heat shock protein (Hsp)90, which was suggested to be related to MMP-9 activation, was measured by Western blot analysis. The ratio of Hsp90 to glyceraldehyde-3-phosphate dehydrogenase was increased in hypoxic (<1%) coculture conditions with TNF-α (P < 0.05). Treatment with geldanamycin and 17-DMAG (Hsp90 inhibitor) suppressed the active form of MMP-9. Cell-to-cell interaction between endothelial cells and monocytes promotes proMMP-9 synthesis and secretion. Hypoxia and inflammation are suggested to play an important role in activating proMMP-9, presumably via Hsp90.

Randomized study on the efficacy and safety of landiolol, an ultra-short-acting ß1-adrenergic blocker, in patients with acute myocardial infarction undergoing primary percutaneous coronary intervention.

BACKGROUND: It is still controversial whether intravenous administration of ß-blocker in the very acute phase of acute myocardial infarction (AMI) is beneficial. Landiolol is an ultra-short-acting ß-blocker that has less effect on blood pressure, but little is known about its efficacy and safety for patients with AMI undergoing primary percutaneous coronary intervention (PCI). METHODS AND RESULTS: A consecutive 96 patients with AMI not manifesting cardiogenic shock were prospectively randomized to landiolol (n = 47) or a control group (n = 49). Continuous administration of landiolol (3 µg·kg(-1)·min(-1) for 24 h) was done just after PCI in the landiolol group, but not in the control group. Heart rate decreased by 9.4 ± 1.7 beats/min after initiation of landiolol (P<0.01), but was unchanged in the control group. Left ventricular ejection fraction assessed 6 months later was greater than that at 2 weeks in the landiolol group (52.0 ± 1.5 vs. 49.1 ± 1.5%, P = 0.01), but remained unchanged in the control group. Left ventricular end-diastolic volume index assessed 6 months later was increased compared with that at 2 weeks in the control group (78.0 ± 2.7 vs. 72.5 ± 2.8 ml/m(2), P = 0.02), whereas it was unchanged in the landiolol group. CONCLUSIONS: Early intravenous administration of landiolol in patients with AMI undergoing PCI is safe and has the potential to improve cardiac function and inhibit cardiac remodeling in the chronic phase.