Yoji Machida

Suppression of Phosphoinositide 3-Kinase Prevents Cardiac Aging in Mice

Background— Heart failure is a typical age-associated disease. Although age-related changes of heart are likely to predispose aged people to heart failure, little is known about the molecular mechanism of cardiac aging. Methods and Results— We analyzed age-associated changes in murine heart and the manner in which suppression of the p110&agr; isoform of phosphoinositide 3-kinase activity modified cardiac aging. Cardiac function declined in old mice associated with the expression of senescence markers. Accumulation of ubiquitinated protein and lipofuscin, as well as comprehensive gene expression profiling, indicated that dysregulation of protein quality control was a characteristic of cardiac aging. Inhibition of phosphoinositide 3-kinase preserved cardiac function and attenuated expression of the senescence markers associated with enhanced autophagy. Suppression of target of rapamycin, a downstream effector of phosphoinositide 3-kinase, also prevented lipofuscin accumulation in the heart. Conclusions— Suppression of phosphoinositide 3-kinase prevented many age-associated changes in the heart and preserved cardiac function of aged mice.

Disruption of Inducible Nitric Oxide Synthase Improves β-Adrenergic Inotropic Responsiveness but Not the Survival of Mice With Cytokine-Induced Cardiomyopathy

Abstract— Transgenic (TG) mice with cardiac-specific overexpression of tumor necrosis factor-&agr; develop congestive heart failure. We have previously reported that short-term inhibition of inducible nitric oxide synthase (iNOS) ameliorates &bgr;-adrenergic hyporesponsiveness in TG mice. To examine whether long-term inhibition of iNOS may rescue TG mice from developing congestive heart failure, we disrupted iNOS gene by crossing TG mice with iNOS knockout mice. Myocardial levels of iNOS protein were significantly increased in TG mice compared with age- and sex-matched wild-type (WT) mice. No iNOS protein was detected in TG mice with the disruption of iNOS. Myocardial levels of endothelial NOS were not different among these mice. To examine the effects of iNOS disruption on myocardial contractility, left ventricular pressure was measured. In TG mice, +dP/dtmax was significantly suppressed, and its &bgr;-adrenergic responsiveness was blunted. As in the case with short-term inhibition of iNOS, the disruption of iNOS gene improved &bgr;-adrenergic inotropic responsiveness in TG mice but not in WT mice. However, the iNOS disruption did not alter myocardial inflammation, ventricular hypertrophy, or the survival of these mice. These results indicate that although myocardial expression of iNOS plays a key role in the attenuation of &bgr;-adrenergic inotropic responsiveness, NO-independent mechanisms might be more important in the development of congestive heart failure.

C-reactive protein-induced production of interleukin-18 in human endothelial cells: a mechanism of orchestrating cytokine cascade in acute coronary syndrome

The circulating interleukin (IL)-18 level is a strong predictor of death from cardiovascular causes in patients with coronary artery disease. However, the mechanisms of IL-18 in orchestrating the cytokine cascade and the accelerator of IL-18 production in atherosclerosis are still unknown. In the present study, we measured the serum concentration of IL-18 and other markers of inflammation in 35 patients with acute coronary syndrome. To determine the mechanism of accelerating IL-18 production, we examined the release of IL-18 in human endothelial cells using human recombinant (hr) C-reactive protein (CRP) as a stimulator of IL-18. Furthermore, we investigated the inhibitory effects of hr IL-10 on IL-18 production by hr CRP in human endothelial cells. Circulating levels of IL-18 were significantly higher in patients with acute myocardial infarction than in patients with unstable angina. Incubation with hr CRP, which was equivalent to the serum concentration in patients with acute coronary syndrome, induced IL-18 release. Treatment with hr IL-10 inhibited IL-18 release in the cells stimulated with hr CRP. The serum level of IL-18 was identified as a marker of severity in acute coronary syndrome. Our findings reveal the possibility that circulating CRP by itself could cause a deterioration of the inflammatory cascade in endothelial cells associated with the upregulation of IL-18. This suggests that CRP may contribute to the mechanism of coronary artery disease in addition to being an incidental product of various types of systemic inflammation.

Effect of persistent activation of phosphoinositide 3-kinase on heart.

AIMS Insulin/insulin-like growth factor-1 (IGF-1) signaling plays an important role in many biological processes. The class IA isoform of phosphoinositide 3-kinase (PI3K) is an important downstream effector of the insulin/IGF-1 signaling pathway. The aim of this study is to examine the effect of persistent activation of PI3K on gene expression and markers of cellular senescence in murine hearts. MAIN METHODS Transgenic mice expressing a constitutively active PI3K in a heart-specific manner were analyzed at the ages of 3 and 20 months. Effects of persistent activation of PI3K on gene expression were comprehensively analyzed using microarrays. KEY FINDINGS Upon comprehensive gene expression profiling, the genes whose expression was increased included those for several heat shock chaperons. The amount and nuclear localization of a forkhead box O (FOXO) protein was increased. In addition, the gene expression of insulin receptor substrate-2 decreased, and that of phosphatase and tensin homolog deleted on chromosome ten (PTEN) increased, suggesting that the persistent activation of PI3K modified the expression of molecules of insulin/IGF-1 signaling. The expression of markers of cellular senescence, such as senescence-associated beta-galactosidase activity, cell cycle inhibitors, proinflammatory cytokines, and lipofuscin, did not differ between old wild-type and caPI3K mice. SIGNIFICANCE The persistent activation of PI3K modified the expression of molecules of insulin/IGF-1 signaling pathway in a transgenic mouse line. Markers of cellular senescence were not changed in the aged mutant mice.

P-11 Suppression of Insulin Signaling Improves Protein Homeostasis and Prevents Cardiac Aging in Mice

P-9 Delayed Enhancement on Cardiac Magnetic Resonance and Clinical, Morphological and ECG Features in Hypertrophic Cardiomyopathy Hiroshi Satoh1, Fumitaka Matoh2, Katsunori Shiraki1, Takeji Saitoh1, Masao Saotome1, Tsuyoshi Urushida1, Hideki Katoh1, Hideharu Hayashi1. 1Internal Medicine III, Hamamatsu University School of Medicine, Japan, 2Department of Cardiology, Omaezaki General Hospital, Japan