The disruption of invariant natural killer T cells exacerbates cardiac hypertrophy and failure caused by pressure overload in mice.

NEW FINDINGS: What is the central question of this study? We questioned whether the disruption of invariant natural killer T (iNKT) cells exacerbates left ventricular (LV) remodelling and heart failure after transverse aortic constriction in mice. What are the main findings and their importance? Pressure overload induced by transverse aortic constriction increased the infiltration of iNKT cells in mouse hearts. The disruption of iNKT cells exacerbated LV remodelling and hastened the transition from hypertrophy to heart failure, in association with the activation of mitogen-activated protein kinase signalling. Activation of iNKT cells modulated the immunological balance in this process and played a protective role against LV remodelling and failure. ABSTRACT: Chronic inflammation is involved in the development of cardiac remodelling and heart failure (HF). Invariant natural killer T (iNKT) cells, a subset of T lymphocytes, have been shown to produce various cytokines and orchestrate tissue inflammation. The pathophysiological role of iNKT cells in HF caused by pressure overload has not been studied. In the present study, we investigated whether the disruption of iNKT cells affected this process in mice. Transverse aortic constriction (TAC) and a sham operation were performed in male C57BL/6J wild-type (WT) and iNKT cell-deficient Jα18 knockout (KO) mice. The infiltration of iNKT cells was increased after TAC. The disruption of iNKT cells exacerbated left ventricular (LV) remodelling and hastened the transition to HF after TAC. Histological examinations also revealed that the disruption of iNKT cells induced greater myocyte hypertrophy and a greater increase in interstitial fibrosis after TAC. The expressions of interleukin-10 and tumour necrosis factor-α mRNA and their ratio in the LV after TAC were decreased in the KO compared with WT mice, which might indicate that the disruption of iNKT cells leads to an imbalance between T-helper type 1 and type 2 cytokines. The phosphorylation of extracellular signal-regulated kinase was significantly increased in the KO mice. The disruption of iNKT cells exacerbated the development of cardiac remodelling and HF after TAC. The activation of iNKT cells might play a protective role against HF caused by pressure overload. Targeting the activation of iNKT cells might thus be a promising candidate as a new therapeutic strategy for HF.

(Pro)renin receptor in skeletal muscle is involved in the development of insulin resistance associated with postinfarct heart failure in mice.

We previously reported that insulin resistance was induced by the impairment of insulin signaling in the skeletal muscle from heart failure (HF) via NAD(P)H oxidase-dependent oxidative stress. (Pro)renin receptor [(P)RR] is involved in the activation of local renin-angiotensin system and subsequent oxidative stress. We thus examined whether (P)RR inhibitor, handle region peptide (HRP), could ameliorate insulin resistance in HF after myocardial infarction (MI) by improving oxidative stress and insulin signaling in the skeletal muscle. C57BL6J mice were divided into four groups: sham operated (Sham, n = 10), Sham treated with HRP (Sham+HRP, 0.1 mg·kg(-1)·day(-1), n = 10), MI operated (MI, n = 10), and MI treated with HRP (MI+HRP, 0.1 mg/kg/day, n = 10). After 4 wk, MI mice showed left ventricular dysfunction, which was not affected by HRP. (P)RR was upregulated in the skeletal muscle after MI (149% of sham, P < 0.05). The decrease in plasma glucose after insulin load was smaller in MI than in Sham (21 ± 2 vs. 44 ± 3%, P < 0.05), and was greater in MI+HRP (38 ± 2%, P < 0.05) than in MI. Insulin-stimulated serine phosphorylation of Akt and glucose transporter 4 translocation were decreased in the skeletal muscle from MI by 48 and 49% of Sham, both of which were ameliorated in MI+HRP. Superoxide production and NAD(P)H oxidase activities were increased in MI, which was inhibited in MI+HRP. HRP ameliorated insulin resistance associated with HF by improving insulin signaling via the inhibition of NAD(P)H oxidase-induced superoxide production in the skeletal muscle. The (P)RR pathway is involved in the development of insulin resistance, at least in part, via the impairment of insulin signaling in the skeletal muscle from HF.

Activation of natural killer T cells ameliorates postinfarct cardiac remodeling and failure in mice.

RATIONALE: Chronic inflammation in the myocardium is involved in the development of left ventricular (LV) remodeling and failure after myocardial infarction (MI). Invariant natural killer T (iNKT) cells have been shown to produce inflammatory cytokines and orchestrate tissue inflammation. However, no previous studies have determined the pathophysiological role of iNKT cells in post-MI LV remodeling. OBJECTIVE: The purpose of this study was to examine whether the activation of iNKT cells might affect the development of LV remodeling and failure. METHODS AND RESULTS: After creation of MI, mice received the injection of either α-galactosylceramide (αGC; n=27), the activator of iNKT cells, or phosphate-buffered saline (n=31) 1 and 4 days after surgery, and were followed during 28 days. Survival rate was significantly higher in MI+αGC than MI+PBS (59% versus 32%, P<0.05). LV cavity dilatation and dysfunction were significantly attenuated in MI+αGC, despite comparable infarct size, accompanied by a decrease in myocyte hypertrophy, interstitial fibrosis, and apoptosis. The infiltration of iNKT cells were increased during early phase in noninfarcted LV from MI and αGC further enhanced them. It also enhanced LV interleukin (IL)-10 gene expression at 7 days, which persisted until 28 days. AntienIL-10 receptor antibody abrogated these protective effects of αGC on MI remodeling. The administration of αGC into iNKT cell-deficient Jα18(-/-) mice had no such effects, suggesting that αGC was a specific activator of iNKT cells. CONCLUSIONS: iNKT cells play a protective role against post-MI LV remodeling and failure through the enhanced expression of cardioprotective cytokines such as IL-10.

Activation of invariant natural killer T cells by α-galactosylceramide ameliorates myocardial ischemia/reperfusion injury in mice.

Invariant natural killer T (iNKT) cells orchestrate tissue inflammation via regulating various cytokine productions. However the role of iNKT cells has not been determined in myocardial ischemia/reperfusion (I/R) injury. The purpose of this study was to examine whether the activation of iNKT cells by α-galactosylceramide (α-GC), which specifically activates iNKT cells, could affect myocardial I/R injury. I/R or sham operation was performed in male C57BL/6J mice. I/R mice received the injection of either αGC (I/R+αGC, n=48) or vehicle (I/R+vehicle, n=49) 30 min before reperfusion. After 24h, infarct size/area at risk was smaller in I/R+αGC than in I/R+vehicle (37.8 ± 2.7% vs. 47.1 ± 2.5%, P<0.05), with no significant changes in area at risk. The numbers of infiltrating myeloperoxidase- and CD3-positive cells were lower in I/R+αGC. Apoptosis evaluated by TUNEL staining and caspase-3 protein was also attenuated in I/R+αGC. Myocardial gene expression of tumor necrosis factor-α and interleukin (IL)-1ß in I/R+αGC was lower to 46% and 80% of that in I/R+vehicle, respectively, whereas IL-10, IL-4, and interferon (IFN)-γ were higher in I/R+αGC than I/R+vehicle by 2.0, 4.1, and 9.6 folds, respectively. The administration of anti-IL-10 receptor antibody into I/R+αGC abolished the protective effects of αGC on I/R injury (infarct size/area at risk: 53.1 ± 5.2% vs. 37.4 ± 3.5%, P<0.05). In contrast, anti-IL-4 and anti-IFN-γ antibodies did not exert such effects. In conclusion, activated iNKT cells by αGC play a protective role against myocardial I/R injury through the enhanced expression of IL-10. Therapies designed to activate iNKT cells might be beneficial to protect the heart from I/R injury.

Mode of death in patients with heart failure and reduced vs. preserved ejection fraction: report from the registry of hospitalized heart failure patients.

BACKGROUND: The mode of death has not been investigated in the registry data of patients with heart failure and reduced ejection fraction (HFREF) vs. preserved ejection fraction (HFPEF). The aim of the present study was therefore to carry out this comparison. METHODS AND RESULTS: The Japanese Cardiac Registry of Heart Failure in Cardiology (JCARE-CARD) prospectively studied the characteristics and treatments in a broad sample of 2,675 patients hospitalized with worsening HF, and followed them for an average of 2.1 years. This study included 323 patients in whom information on both the mode of death and left ventricular EF on echocardiography could be obtained. The mode of death was cardiovascular (CV) in 63% (including 17% sudden, 36% HF, 3% myocardial infarction, and 3% stroke), non-CV in 23%, and unknown in 14%. The prevalence of CV death including sudden death was high in patients with HFREF compared to HFPEF (68% vs. 58%, P=0.020). HF death, the most common mode of death, was similar between groups (37% vs. 35%, P=0.694). In contrast, non-CV mortality was significantly higher in HFPEF than those with HFREF (28% vs. 18%, P=0.021). CONCLUSIONS: In 60-70% of deaths the mode was CV, and HF death was the most common mode of death in either HFREF or HFPEF. The prevalence of sudden death was lower, and that of non-CV death higher, in HFPEF compared with HFREF.

Trimetazidine improves left ventricular global longitudinal strain value in patients with heart failure with reduced ejection fraction due to ischemic heart disease.

Heart failure with reduced ejection fraction (HFrEF) due to ischemic heart disease (IHD) showed a progressive decline in left ventricular contractile function. However, no previous study has examined the left ventricular global longitudinal strain (LV GLS) parameter that represents LV contractile function. We investigated whether trimetazidine could improve the LV GLS value in patients with HFrEF due to IHD. We performed a double-blind, randomized controlled trial (RCT) including 26 patients with HFrEF due to stable IHD who were given modified-release trimetazidine 35 mg twice per day (n = 13) or placebo (n = 13) for 3 months in addition to standard medication. Left ventricular systolic function including GLS values was assessed at baseline and after 3 months using echocardiography. A total of 25 participants (13 control and 12 trimetazidine groups) were recruited with a baseline average age of 57.1 ± 10 years, and LV ejection fraction (LVEF) value of 34.6% ± 4.4%, and a GLS value of 7.4% ± 2.1%. Baseline clinical characteristics and echocardiogram were similar between the two groups. There was significant GLS improvement in the trimetazidine group (-6.9% ± 2.4% to -8.4% ± 2.6%, p = 0.000), but no significant differences were noted in the control group. The GLS improvement was significantly higher in the trimetazidine group than the control (1.5% + 0.9% vs. -0.7% + 1.7%, p = 0.001). No adverse drug reactions from the administration of trimetazidine in this study. Trimetazidine may improve GLS values in patients with HFrEF due to IHD.

Effects of coenzyme Q10 supplementation on diastolic function in patients with heart failure with preserved ejection fraction.

Heart failure with preserved ejection fraction (HFpEF) is a leading cause of morbidity and mortality without an established treatment. Diastolic dysfunction, the hallmark of HFpEF, is associated with altered myocardial bioenergetics. No previous study has examined the effects of coenzyme Q10 (CoQ10) on left ventricle (LV) diastolic function in patients with HFpEF. We investigated whether CoQ10 could improve LV diastolic function in patients with HFpEF. We performed a randomized controlled trial (RCT) using pretest and posttest control groups of 30 patients with HFpEF. The patients received either CoQ10 100 mg three times a day or no CoQ10 in addition to routine treatment for 30 days. Echocardiographic study was performed at baseline and follow-up. LV diastolic function was evaluated by two dimensional and Doppler echocardiography as follows; average E/e׳, septal and lateral e׳velocity, and left atrium volume index (LAVI). A total of 28 patients completed the study. A statistically significant improvement was observed in the CoQ10 treatment group in terms between groups (∆E/e׳ ‒ 3.6 vs. ‒ 2.4; p = 0.28) and (∆LAVI ‒ 5.4 vs. ‒ 4.4; p = 0.83). Short term CoQ10 supplementation provided no additional benefits in improving LV diastolic function in patients with HFpEF.