Tsuyoshi Sakoda

Adaptive response of the heart to long-term anemia induced by iron deficiency

Anemia is common in patients with chronic heart failure and an independent predictor of poor prognosis. Chronic anemia leads to left ventricular (LV) hypertrophy and heart failure, but its molecular mechanisms remain largely unknown. We investigated the mechanisms, including the molecular signaling pathway, of cardiac remodeling induced by iron deficiency anemia (IDA). Weanling Sprague-Dawley rats were fed an iron-deficient diet for 20 wk to induce IDA, and the molecular mechanisms of cardiac remodeling were evaluated. The iron-deficient diet initially induced severe anemia, which resulted in LV hypertrophy and dilation with preserved systolic function associated with increased serum erythropoietin (Epo) concentration. Cardiac STAT3 phosphorylation and VEGF gene expression increased by 12 wk of IDA, causing angiogenesis in the heart. Thereafter, sustained IDA induced upregulation of cardiac hypoxia inducible factor-1alpha gene expression and maintained upregulation of cardiac VEGF gene expression and cardiac angiogenesis; however, sustained IDA promoted cardiac fibrosis and lung congestion, with decreased serum Epo concentration and cardiac STAT3 phosphorylation after 20 wk of IDA compared with 12 wk. Upregulation of serum Epo concentration and cardiac STAT3 phosphorylation is associated with a beneficial adaptive mechanism of anemia-induced cardiac hypertrophy, and later decreased levels of these molecules may be critical for the transition from adaptive cardiac hypertrophy to cardiac dysfunction in long-term anemia. Understanding the mechanism of cardiac maladaptation to anemia may lead to a new strategy for treatment of chronic heart failure with anemia.

OCT Assessment of Thin-Cap Fibroatheroma Distribution in Native Coronary Arteries

OBJECTIVESnWe evaluated the geographic distribution of thin-cap fibroatheromas (TCFAs) in the coronary arteries using optical coherence tomography (OCT), a high-resolution imaging modality.nnnBACKGROUNDnPlaque rupture is the most frequent cause of acute myocardial infarction (AMI). It has been recognized that TCFA is the primary plaque type at the site of plaque rupture.nnnMETHODSnWe performed 3-vessel OCT examinations in 55 patients: 35 AMI and 20 stable angina pectoris patients. The criteria for TCFA in an OCT image was a lipid-rich plaque with fibrotic cap thickness <65 microm. The distance between each TCFA location and the respective coronary artery ostium was measured with motorized OCT imaging pullback. The total length of all 3 coronary arteries imaged by OCT pullbacks was 82 +/- 21 mm in the left anterior descending coronary artery (LAD), 67 +/- 26 mm in the left circumflex coronary artery (LCx), and 104 +/- 32 mm in the right coronary artery (RCA).nnnRESULTSnOCT detected 94 TCFAs in 165 coronary arteries. The minimum fibrous-cap thickness of TCFAs was 57.4 +/- 5.4 microm in AMI patients, and 55.9 +/- 7.3 microm in stable angina pectoris patients (p = 0.4). Of the total of 94 TCFAs, 28 were detected in the LAD, 18 in the LCx, and 48 in the RCA. Most LAD TCFAs were located between 0 and 30 mm from the LAD ostium (76%). Conversely, LCx and RCA TCFAs were evenly distributed throughout the entire coronary length. The clustering of the TCFAs was similar in culprit segments as compared with nonculprit segments. In AMI patients, most LAD TCFAs were distributed near side branches, mainly positioned opposite the side branch bifurcation.nnnCONCLUSIONSnThree-vessel OCT imaging showed that TCFAs tend to cluster in predictable spots within the proximal segment of the LAD, but develop relatively evenly in the LCx and RCA arteries.

Serum interleukin-6 and C-reactive protein are markedly elevated in acute decompensated heart failure patients with left ventricular systolic dysfunction.

Cytokines play important roles in heart failure (HF). We examined whether cytokine levels are different in acute decompensated heart failure (ADHF) patients between with left ventricular systolic dysfunction (LVSDF) and with preserved LV ejection function (PLVEF). We studied 81 HF patients who were admitted to our hospital with acute decompensation. They were divided into two groups: LVSDF (LVEF)<45% and PLVEF (LVEF45%). Serum interleukin-6 (IL-6), highly sensitive C-reactive protein (hsCRP), tumor necrosis factor alpha (TNF-alpha), and IL-18 and plasma brain natriuretic peptide (BNP) were measured on admission and at discharge. On admission, IL-6 and hsCRP were higher in LVSDF than in PLVEF. IL-6 and hsCRP decreased after treatment in LVSDF, but not in PLVEF, while plasma BNP levels decreased in both HF with treatment. There was no difference in TNF-alpha or in IL-18 level between LVSDF and PLVEF, and they did not change after treatment in either group. In conclusion, cytokine profiles were different in ADHF between those with LVSDF and PLVEF. Activation of IL-6-hsCRP pathway may play a specific role in ADHF with LVSDF.

Deficiency of Nectin-2 Leads to Cardiac Fibrosis and Dysfunction Under Chronic Pressure Overload

The intercalated disc, a cell-cell contact site between neighboring cardiac myocytes, plays an important role in maintaining the homeostasis of the heart by transmitting electric and mechanical signals. Changes in the architecture of the intercalated disc have been observed in dilated cardiomyopathy. Among cell-cell junctions in the intercalated disc, adherens junctions are involved in anchoring myofibrils and transmitting force. Nectins are Ca2+-independent, immunoglobulin-like cell-cell adhesion molecules that exist in adherens junctions. However, the role of nectins in cardiac homeostasis and integrity of the intercalated disc are unknown. Among the isoforms of nectins, nectin-2 and -4 were expressed at the intercalated disc in the heart. Nectin-2–knockout mice showed normal cardiac structure and function under physiological conditions. Four weeks after banding of the ascending aorta, cardiac function was significantly impaired in nectin-2–knockout mice compared with wild-type mice, although both nectin-2–knockout and wild-type mice developed similar degrees of cardiac hypertrophy. Banded nectin-2–knockout mice displayed cardiac fibrosis more evidently than banded wild-type mice. The disruption of the intercalated discs and disorganized myofibrils were observed in banded nectin-2–knockout mice. Furthermore, the number of apoptotic cardiac myocytes was increased in banded nectin-2–knockout mice. In the hearts of banded nectin-2–knockout mice, Akt remained at lower phosphorylation levels until 2 weeks after banding, whereas c-Jun N-terminal kinase and p38 mitogen-activated protein kinase were highly phosphorylated compared with those of wild-type mice. These results indicate that nectin-2 is required to maintain structure and function of the intercalated disc and protects the heart from pressure-overload–induced cardiac dysfunction.

Hyperglycemia induced cell growth and gene expression via the serum response element through RhoA and Rho-kinase in vascular smooth muscle cells.

The impressive correlation between cardiovascular disease and alterations in glucose metabolism has raised the likelihood that atherosclerosis, heart failure, and type 2 diabetes may share common antecedents. Postprandial hyperglycemia has been shown to play an important role on the onset and development of heart failure and cerebral infarction in several large-scale clinical trials. Recently, chronic hyperglycemia has been reported to enhance the vasoconstrictor response by Rho-kinase. We have previously reported that phenylephrine enhanced the vasoconstrictor response in a spontaneous diabetes mellitus OLETF (Otsuka-Long-Evane-Tokushima fatty) rat model. However, the mechanism of hyperglycemia in these reactions, particularly the influence of hyperglycemia on the signal transduction pathway, is still not well understood. We, therefore, examined the effect of hyperglycemia on the cell growth and gene expression of rat aortic smooth-muscle cells (RASMCs). Hyperglycemia accelerated the growth of RASMCs in a concentration-dependent manner. Furthermore, the c-fos gene expression was also increased by hyperglycemia. Phenylephrine activated the c-fos gene expression. Hyperglycemia augmented the phenylephrine-induced c-fos gene expression synergistically in a dose dependent manner. The deletion analysis revealed that the c-fos serum response element (SRE) accounts for the c-fos gene expression. RhoA, and Rho-kinase were involved in hyperglycemia-induced c-fos gene expression. An HMG-CoA reductase inhibitor, Pitavastatin, inhibited these hyperglycemia-augmented reactions by inhibiting RhoA. Hyperglycemia itself increased the cell growth and gene expression. Furthermore, it modifies and augments the cell growth and gene expression by α1-AR-mediated stimulation. Statin might therefore be effective for the treatment of hyperglycemia-induced cardiovascular dysfunction.

Lentiviral vector-mediated gene transfer to endotherial cells compared with adenoviral and retroviral vectors.

Abstract Human immunodeficiency virus (HIV, lentivirus) vector has attractive features for gene therapy, including the ability to transduce non‐dividing cells and long‐term transgene expression. We have already reported that lentivirus vector can transduce well‐differentiated rat cardiac myocytes. Endothelial cells (EC) are an attractive target for gene therapy, both for the treatment of cardiovascular disease and for the systemic delivery of recombinant gene products directly into the circulation. There are several reports regarding application of adenovirus and retrovirus based vectors to EC. However, there have been few reports which show the effect to lentivirus‐mediated gene transfer efficiency, compared with adenovirus and retrovirus. In this study, bovine aortic endothelial cells (BAECs) were infected, in vitro, with these virus vectors. Transduction efficiency (TE) of β‐Gal gene transfer in BAECs by adenovirus, lentivirus, or retrovirus at MOI10 (Multiplicity of infection) (determined on Hela cells) is 69±11, 33±8, or 22±6% respectively. In adenovirus and lentivirus, almost 100% of BAECs were transduced at MOI 50. However, in retrovirus, TE showed only 48±6% at MOI 50 and no increase at MOI 100. The percentage of β‐Gal positive cells was decreased rapidly at longer passage of cells after being transduced by adenovirus. However, lentivirus and retrovirus showed sustained higher percentage of positive cells. Furthermore, transduction by lentiviral vectors had no significant effect on viability of BAECs. Our results indicate that lentivirus showed high‐level and long term gene expression in BAECs. Lentivirus can be an effective vector for the ex vivo, genetically modified EC implantation and in vivo gene therapy.

Circadian expression of plasminogen activator inhibitor-1 in angiotensin II type 1a receptor knockout mice.

Both the peripheral biological clock and the renin-angiotensin system regulate mRNA expression of plasminogen activator inhibitor-1 (PAI-1). Our objective was to determine whether angiotensin II (Ang II) type 1 (AT1) receptor-mediated signaling contributes to the development of circadian expression of PAI-1 and clock genes in the heart, aorta, liver, and kidney. We sacrificed AT1a receptor knockout (AT1a-KO) and wild-type (WT) 12 week-old mice every 4 hr. We examined mRNA expression for PAI-1 and clock genes (Per2, Bmal1, and Clock) in heart, aorta, liver, and kidney by using the quantitative reverse transcription-polymerase chain reaction. PAI-1 mRNA showed circadian oscillation with a peak occurring during the light phase in the heart, liver, aorta, and kidney of WT mice. Peak expression of PAI-1 in the liver and aorta was decreased in AT1a-KO mice. On the other hand, cardiac PAI-1 expression in AT1a-KO mice was reduced in the dark phase, during which time its expression level was low. There were no significant differences between WT and AT1a-KO mice in renal PAI-1 expression. Clock genes oscillated synchronously in WT and AT1a-KO mice, and there were no significant differences between the WT and the AT1a-KO mice in their expression. Plasma angiotensin II showed little oscillation in the WT mice. We conclude that AT1a receptor-mediated Ang II signaling modulates the circadian expression of PAI-1 in an organ-specific manner. The effect of the renin-angiotensin system on PAI-1 expression appears to be independent of peripheral clock gene expression.

Mechanical stretch induced interleukin-18 (IL-18) expression through Angiotensin subtype 1 receptor (AT1R) and endothelin-1 in cardiomyocytes.

Abstract Interleukin‐18 (IL‐18) is a proinflammatory cytokine with multiple biological functions. We and others have demonstrated that an increased level of circulating IL‐18 is one of the risk factors for cardiovascular diseases. Endothelin‐1 (ET‐1) has been reported to be a potent hypertrophy‐promoting factor through RhoA and Rho‐Kinase. Mechanical stretch induces a hypertrophic response, partly through the production of ET‐1 through Endothelin A receptor (ETAR). Moreover, it has also been reported that mechanical stretch induces cardiac hypertrophy through Angiotensin subtype 1 receptor (AT1R). However, the mechanism by which the IL‐18 gene expression is regulated in cardiomyocytes has not yet been fully understood. This study was designed to elucidate the functional significance of IL‐18 gene expression in response to mechanical stretch. Neonatal rat cardiomyocytes cultured on silicone dishes were subjected to stretch. The moderate 20% mechanical stretch resulted in the elevation of IL‐18 expression in a time‐dependent manner with the maximal level achieved 36 hours after the stretch. Olmesartan, AT1R antagonist inhibited stretch‐induced IL‐18 expression. ETAR blockade BQ123 inhibited stretch‐induced IL‐18 expression. However, the Endothelin B receptor (ETBR) receptor blockade BQ788 did not inhibit this reaction. ET‐1 induced IL‐18 expression, with a peak induction after 4 hours of incubation. These results might suggest that stretch stimulation of cardiomyocytes induced ET‐1 and, subsequently, ET‐1 up‐regulated the IL‐18 expression. Furthermore, Fasudil, a Rho‐Kinase inhibitor, and Simvastatin, a HMG‐CoA reductase inhibitor, led to a significant reduction in mechanical stretch‐induced IL‐18 expression. These results indicated, for the first time, that IL‐18 expression is induced by mechanical stretch in cardiomyocytes via the ETAR, AT1R, and the Rho/Rho‐K pathways. The induction of IL‐18 from cardiomyocytes by mechanical stress might cause the deterioration of cardiac functions in autocrine and paracrine fashion. The inhibition of IL‐18 expression induced by mechanical stress might be one of the mechanisms that account for the beneficial cardiovascular effects of AT1R antagonist, ETAR blockade, Statin, and Rho‐Kinase inhibitor.

Decrease in serum adiponectin levels in response to treatment predicts good prognosis in acute decompensated heart failure.

J Clin Hypertens (Greenwich).

The mechanism of distinct diurnal variations of renin-angiotensin system in aorta and heart of spontaneously hypertensive rats.

Diurnal variations in plasminogen activator inhibitor-1 mRNA expression are different between the spontaneously hypertensive rats (SHRs) and the Wistar-Kyoto (WKY) rats, and between the aorta and the heart. To elucidate the mechanisms, we examined diurnal changes in the circulating renin-angiotensin system in the SHR and WKY rats. Diurnal variations in plasma renin activity (PRA), plasma angiotensin I, and aldosterone concentrations were similar between the SHR and WKY rats. On the other hand, plasma angiotensin II (Ang II) concentration in the SHR was lower than that in the WKY rats at most time points, but increased to the level of the WKY rats in the late light phase. Treatment with AT1 receptor antagonist candesartan increased plasma Ang II concentration except at ZT 8 and lessened its diurnal variation in the SHR. At the peak in plasma Ang II in the SHR, Ang II regulated genes such as transforming growth factor-β1 and p22phox were upregulated in the aorta. On the other hand, these genes were upregulated throughout the day in the heart of SHR. Candesartan treatment increased AT1a receptor mRNA expression in the heart but not in the aorta of SHR. These findings suggest that an AT1 receptor-mediated mechanism might cause a surge in plasma Ang II concentration at the late light phase in the SHR. Homologous down-regulation of AT1a receptor by Ang II may dampen the effect of a surge in plasma Ang II concentration in the heart of SHR.