Tatsuro Kitahara

High-mobility group box 1 restores cardiac function after myocardial infarction in transgenic mice

AIMS High-mobility group box 1 (HMGB1) is a nuclear DNA-binding protein and is released from necrotic cells, inducing inflammatory responses and promoting tissue repair and angiogenesis. To test the hypothesis that HMGB1 enhances angiogenesis and restores cardiac function after myocardial infarction (MI), we generated transgenic mice with cardiac-specific overexpression of HMGB1 (HMGB1-Tg) using alpha-myosin heavy chain promoter. METHODS AND RESULTS The left anterior descending coronary artery was ligated in HMGB1-Tg and wild-type littermate (Wt) mice. After coronary artery ligation, HMGB1 was released into circulation from the necrotic cardiomyocytes of HMGB1-overexpressing hearts. The size of MI was smaller in HMGB1-Tg than in Wt mice. Echocardiography and cardiac catheterization demonstrated that cardiac remodelling and dysfunction after MI were prevented in HMGB1-Tg mice compared with Wt mice. Furthermore, the survival rate after MI of HMGB1-Tg mice was higher than that of Wt mice. Immunohistochemical staining revealed that capillary and arteriole formation after MI was enhanced in HMGB1-Tg mice. CONCLUSION We report the first in vivo evidence that HMGB1 enhances angiogenesis, restores cardiac function, and improves survival after MI. These results may provide a novel therapeutic approach for left ventricular dysfunction after MI.

Soluble Receptor for advanced glycation end products (RAGE) is a prognostic factor for heart failure.

BACKGROUND We recently reported that serum levels of pentosidine, one of the well-defined advanced glycation end products (AGE), was an independent prognostic factor for heart failure. Receptor for AGEs (RAGE) is expressed in a variety of tissues, and RAGE has a C-truncated secretory isoform of the receptor protein, termed soluble RAGE. In the present study, we measured serum soluble RAGE levels in patients and examined whether serum soluble RAGE predicts prognosis in patients with heart failure. METHODS AND RESULTS Serum soluble RAGE concentration was measured in 160 patients with heart failure by a competitive enzyme-linked immunosorbent assay. Patients were prospectively followed during a median follow-up period of 872 days with end points of cardiac death or rehospitalization. Serum soluble RAGE level increased with advancing New York Heart Association functional class. Serum soluble RAGE level was also higher in patients with cardiac events than in event free patients. From the receiver operating characteristic curve analysis, the cutoff value of serum soluble RAGE level was determined as 1220 pg/mL. Kaplan-Meier analysis clearly demonstrated that the high soluble RAGE group had a significantly higher incidence of cardiac events than occurred in the low serum soluble RAGE group (P = .0004). In the multivariate Cox proportional hazard analysis, soluble RAGE and serum pentosidine were independent risk factors for cardiac events (soluble RAGE: HR 1.90, 95% CI 1.16-3.09, P = .010; pentosidine: HR 1.59, 95% CI 1.11-2.29, P = .012). CONCLUSIONS Serum soluble RAGE level is an independent prognostic factor for heart failure, and this novel marker may be useful for risk stratification of patients with heart failure.

Diacylglycerol kinase-ε restores cardiac dysfunction under chronic pressure overload: a new specific regulator of Gαq signaling cascade

Galpha(q) protein-coupled receptor (GPCR) signaling pathway, which includes diacylglycerol (DAG) and protein kinase C (PKC), plays a critical role in cardiac hypertrophy. DAG kinase (DGK) catalyzes DAG phosphorylation and controls cellular DAG levels, thus acting as a regulator of GPCR signaling. It has been reported that DGKepsilon acts specifically on DAG produced by inositol cycling. In this study, we examined whether DGKepsilon prevents cardiac hypertrophy and progression to heart failure under chronic pressure overload. We generated transgenic mice with cardiac-specific overexpression of DGKepsilon (DGKepsilon-TG) using an alpha-myosin heavy chain promoter. There were no differences in cardiac morphology and function between wild-type (WT) and DGKepsilon-TG mice at the basal condition. Either continuous phenylephrine infusion or thoracic transverse aortic constriction (TAC) was performed in WT and DGKepsilon-TG mice. Increases in heart weight after phenylephrine infusion and TAC were abolished in DGKepsilon-TG mice compared with WT mice. Cardiac dysfunction after TAC was prevented in DGKepsilon-TG mice, and the survival rate after TAC was higher in DGKepsilon-TG mice than in WT mice. Phenylephrine- and TAC-induced DAG accumulation, the translocation of PKC isoforms, and the induction of fetal genes were blocked in DGKepsilon-TG mouse hearts. The upregulation of transient receptor potential channel (TRPC)-6 expression after TAC was attenuated in DGKepsilon-TG mice. In conclusion, these results demonstrate the first evidence that DGKepsilon restores cardiac dysfunction and improves survival under chronic pressure overload by controlling cellular DAG levels and TRPC-6 expression. DGKepsilon may be a novel therapeutic target to prevent cardiac hypertrophy and progression to heart failure.

Diacylglycerol kinase ζ inhibits myocardial atrophy and restores cardiac dysfunction in streptozotocin-induced diabetes mellitus

BackgroundActivation of the diacylglycerol (DAG)-protein kinase C (PKC) pathway has been implicated in the pathogenesis of a number of diabetic complications. Diacylglycerol kinase (DGK) converts DAG to phosphatidic acid and acts as an endogenous regulator of PKC activity. Akt/PKB is associated with a downstream insulin signaling, and PKCβ attenuates insulin-stimulated Akt phosphorylation.Methods and ResultsWe examined transgenic mice with cardiac-specific overexpression of DGKζ (DGKζ-TG) compared to wild type (WT) mice in streptozotocin-induced (STZ, 150 mg/kg) diabetic and nondiabetic conditions. After 8 weeks, decreases in heart weight and heart weight/body weight ratio in diabetic WT mice were inhibited in DGKζ-TG mice. Echocardiography at 8 weeks after STZ-injection demonstrated that decreases in left ventricular end-diastolic diameter and fractional shortening observed in WT mice were attenuated in DGKζ-TG mice. Thinning of the interventricular septum and the posterior wall in diabetic WT hearts were blocked in DGKζ-TG mice. Reduction of transverse diameter of cardiomyocytes isolated from the left ventricle in diabetic WT mice was attenuated in DGKζ-TG mice. Cardiac fibrosis was much less in diabetic DGKζ-TG than in diabetic WT mice. Western blots showed translocation of PKCβ and δ isoforms to membrane fraction and decreased Akt/PKB phosphorylation in diabetic WT mouse hearts. However in diabetic DGKζ-TG mice, neither translocation of PKC nor changes Akt/PKB phosphorylation was observed.ConclusionDGKζ modulates intracellular signaling and improves the course of diabetic cardiomyopathy. These data may suggest that DGKζ is a new therapeutic target to prevent or reverse diabetic cardiomyopathy.

Serum YKL-40 Predicts Adverse Clinical Outcomes in Patients With Chronic Heart Failure

BACKGROUND Human cartilage glycoprotein-39 (YKL-40), a novel inflammatory marker, is secreted into circulation by macrophages, neutrophils, chondrocytes, vascular smooth muscle cells and cancer cells. Circulating levels of YKL-40 are related to the degree of inflammation, tissue remodeling, fibrosis, and cancer progression. METHODS AND RESULTS We examined serum YKL-40 levels in 121 patients with chronic heart failure (CHF) and 39 control subjects. The patients were followed up to register cardiac events for a mean of 720 days. Serum YKL-40 levels were measured by sandwich enzyme-linked immunoassay. Serum YKL-40 was significantly higher in New York Heart Association (NYHA) Class III/IV patients than control subjects and NYHA Class I/II patients (P < .0001). Serum YKL-40 was also higher in patients with cardiac events than in event-free patients (P = .0023). Cutoff value of YKL-40 was determined by receiver operating characteristic curve analysis. Kaplan-Meier analysis demonstrated that high level of YKL-40 was associated with higher rates of cardiac events than low levels of YKL-40 (P = .003). The multivariate Cox hazard analysis demonstrated that serum YKL-40 level was an independent prognostic factor of cardiac events (hazard ratio 2.085, 95% confidence interval 1.233-3.499, P < .0048). CONCLUSIONS Serum YKL-40, a new marker of inflammation, was increased in CHF, and YKL-40 detected high risk patients for adverse outcomes in CHF.

Relation of Serum Heat Shock Protein 60 Level to Severity and Prognosis in Chronic Heart Failure Secondary to Ischemic or Idiopathic Dilated Cardiomyopathy

Heat shock protein (HSP) 60 is induced by a variety of stressors, including oxidative stress and inflammation, and it plays a protective role against stress-induced cardiomyocyte injury. Recently, it has been reported that HSP 60 exists in the circulation. Chronic heart failure (CHF) is characterized by systemic abnormalities, and the myocardium is exposed to various stressors. However, the clinical significance of serum HSP 60 has not been examined in CHF. Therefore, the purpose of this study was to examine whether HSP 60 is correlated with the severity of CHF and whether HSP 60 can predict clinical outcomes in patients with CHF. Serum HSP 60 levels were measured in 112 patients with CHF and 62 control subjects. Serum HSP 60 levels were higher in patients with CHF than in control subjects and increased with advancing New York Heart Association functional class. There were 37 cardiac events during a mean follow-up period of 569 +/- 476 days (range 17 to 1,986). Serum HSP 60 levels were higher in patients with cardiac events than in event-free patients. Patients were divided into 4 groups on the basis of HSP 60 level. Cox proportional-hazards regression analysis and Kaplan-Meier analysis revealed that the fourth quartile was associated with the greatest risk for cardiac events. In conclusion, serum HSP 60 level was related to the severity of CHF and associated with a high risk for adverse cardiac events in patients CHF.

Long pentraxin PTX3 exacerbates pressure overload-induced left ventricular dysfunction.

Background Left ventricular hypertrophy is enhanced by an inflammatory state and stimulation of various cytokines. Pentraxin 3 (PTX3) is rapidly produced in response to inflammatory signals, and high plasma PTX3 levels are seen in patients with heart failure. This study aimed to examine the influence of PTX3 on cardiac hypertrophy and left ventricular dysfunction with respect to pressure overload. Methods and Results PTX3 systemic knockout (PTX3-KO) mice, transgenic mice with cardiac-specific overexpression of PTX3 (PTX3-TG), and the respective wild-type (WT) littermate mice were subjected to transverse aortic constriction (TAC) or a sham operation. Cardiac PTX3 expression increased after TAC in WT mice. In vitro, hydrogen peroxide induced the expression of PTX3 in both cardiac myocytes and cardiac fibroblasts. Recombinant PTX3 phosphorylated extracellular signal–regulated kinase 1/2 (ERK1/2) in cardiac fibroblasts. Phosphorylation of cardiac ERK1/2 and nuclear factor kappa-B after TAC was attenuated in the PTX3-KO mice but was enhanced in the PTX3-TG mice compared with WT mice. Interleukin-6 and connective tissue growth factor production was lower in the PTX3-KO mice than in the WT mice, but this was augmented in the PTX3-TG mice than in the WT mice. Echocardiography revealed that adverse remodeling with left ventricular dysfunction, as well as with increased interstitial fibrosis, was enhanced in PTX3-TG mice, while these responses were suppressed in PTX3-KO mice. Conclusion The local inflammatory mediator PTX3 directly modulates the hypertrophic response and ventricular dysfunction following an increased afterload.

Serum Midkine as a Predictor of Cardiac Events in Patients With Chronic Heart Failure

BACKGROUND Midkine, a heparin-binding growth factor, has various functions such as migration of inflammatory cell and anti-apoptotic effect. Invasion of inflammatory cell and cardiomyocyte apoptosis are involved in development and progression of heart failure (HF). However, the relationship between midkine and HF has not been previously examined. Therefore, we examined clinical significance of serum midkine levels to determine the prognosis of HF patients. METHODS AND RESULTS Serum levels of midkine were measured at admission in 216 consecutive patients hospitalized for HF and 60 control subjects. Patients were prospectively followed during a mean follow-up period of 653 +/- 375 days with the end points of cardiac death and progressive HF requiring rehospitalization. Serum concentrations of midkine were significantly higher in patients with HF than in controls. Patients with cardiac events had significantly higher concentrations of midkine than those without cardiac events. Kaplan-Meier analysis revealed that cardiac event rates increased markedly as midkine levels rose. Furthermore in the multivariate analysis, after adjustment for age, gender ,and complications, midkine was the independent predictor of cardiac events. CONCLUSION Serum midkine levels are increased in HF patients, and midkine is a novel marker for risk stratifying HF patients.

High serum level of neopterin is a risk factor of patients with heart failure

Serum neopterin concentration was measured in 198 patients with chronic heart failure (CHF) and 62 control subjects by ELISA. Patients were prospectively followed during a median follow-up period of 745 days with end points of cardiac death or re-hospitalization due to progressive heart failure. Serum concentration of neopterin increased with advancing New York Heart Association (NYHA) functional class (P<0.001). High neopterin group had a significantly higher incidence of cardiac events than low neopterin group (P<0.0001). In the multivariate Cox analysis, serum neopterin concentration was an independent risk factor for cardiac events (hazard ratio 1.70, 95%CI 1.16-2.50, P=0.0068). Serum neopterin concentration is a novel prognostic marker for CHF.

Midkine exacerbates pressure overload-induced cardiac remodeling.

Midkine is a multifunctional growth factor, and its serum levels are increased with the functional severity of heart failure. This study aimed to examine the role of midkine in heart failure pathogenesis. Midkine expression levels were increased in the kidney and lung after transverse aortic constriction (TAC) surgery, but not sufficiently increased in the heart. After TAC, phosphorylation of extracellular signal-regulated kinase1/2 and AKT, and the expression levels of foetal genes in the heart were considerably increased in transgenic mice with cardiac-specific overexpression of midkine (MK-Tg) compared with wild-type (WT) mice. MK-Tg mice showed more severe cardiac hypertrophy and dysfunction, and showed lower survival rate after TAC than WT mice. We conclude that midkine plays a critical role in cardiac hypertrophy and remodelling.