Wanling Xuan

Detrimental effect of fractalkine on myocardial ischaemia and heart failure

AIMS Fractalkine (FKN) is a newly identified membrane-bound chemokine; its role in myocardial ischaemia and heart failure is largely unknown. We attempted to investigate the role of FKN in myocardial ischaemia and ischaemia or pressure overload-induced ventricular remodelling and heart failure. METHODS AND RESULTS FKN-induced changes of heart failure-related genes in cultured rat cardiac cells and the effect of FKN on cultured cardiomyocyte injury during anoxia/reoxygenation (A/R) were examined. The direct influence of FKN neutralization on heart failure and the potential mechanism was also investigated. In mice with failing hearts, myocardial FKN expression was correlated with the lung weight/body weight ratio, left ventricular fractional shortening, and brain natriuretic peptide expression. In cultured rat cells, exposure to FKN increased natriuretic peptide A expression in cardiomyocytes, matrix metalloproteinase-9 expression in fibroblasts, and intercellular adhesion molecule-1 expression in microvascular endothelial cells. FKN also promoted cardiomyocyte damage during A/R and neutralizing FKN antibody treatment improved heart failure induced by myocardial infarction or pressure overload. Neutralizing FKN or its receptor inhibited the activation of mitogen-activated protein kinases (MAPKs) in hypoxic cardiomyocytes or ischaemic myocardium. CONCLUSION FKN promotes myocardial injury and accelerates the progress of heart failure, which is associated with the activation of MAPKs.

Resveratrol improves myocardial ischemia and ischemic heart failure in mice by antagonizing the detrimental effects of fractalkine

Objectives:To test the hypothesis that resveratrol would improve cardiac remodeling by inhibiting the detrimental effects of fractalkine. We previously reported that fractalkine exacerbates heart failure. Furthermore, this study sought to determine whether resveratrol targets fractalkine to improve myocardial ischemia and cardiac remodeling. Design:Randomized and controlled laboratory investigation. Setting:Research laboratory. Subjects:Neonatal rat cardiac cells and C57BL/6 mice. Interventions:Cardiac cells were treated with recombinant mouse soluble fractalkine for 24 hrs or pretreated with 25 µM resveratrol. Cardiomyocytes were exposed to anoxia/reoxygenation, H2O2, or pretreatment with resveratrol. Ex vivo murine hearts were perfusioned with soluble fractalkine or pretreated with resveratrol after global ischemia. Mice were subjected to the left coronary artery ligation to induce myocardial infarction and randomized to treatment with resveratrol or vehicle alone for 42 days. Measurements and Main Results:In a murine myocardial infarction model, we found that resveratrol increased survival and delayed the progression of cardiac remodeling evaluated by serial echocardiography. At 6 wks, the heart weight/body weight ratio, lung weight/body weight ratio, and old infarct size were significantly smaller in resveratrol-treated mice than in untreated myocardial infarction mice. In cultures of neonatal rat cells, exposure to soluble fractalkine increased the atrial natriuretic peptide expression by cardiomyocytes, matrix metalloproteinase-9 and procollagen expression by fibroblasts, and intercellular adhesion molecule-1 expression by microvascular endothelial cells, while it decreased autophagy in cardiomyocytes. All these effects were blocked by coculture with resveratrol. The methyl thiazolyl tetrazolium assay showed that soluble fractalkine reduced the viability of cultured cardiomyocytes during exposure to anoxia/reoxygenation or H2O2, while pretreatment with resveratrol blocked this effect. Perfusion of ex vivo murine hearts with soluble fractalkine after global ischemia led to an increase of infarct size, which was prevented by pretreatment with resveratrol. Conclusion:Resveratrol alleviates the deleterious effects of fractalkine on myocardial ischemia and thus reduces subsequent cardiac remodeling.

Late-phase detection of recent myocardial ischaemia using ultrasound molecular imaging targeted to intercellular adhesion molecule-1

AIMS in this study, we attempted to detect a recent myocardial ischaemic event using ultrasound molecular imaging (UMI) with microbubbles (MB) targeted to intercellular adhesion molecule-1 (ICAM-1) in the late phase of reperfusion. METHODS AND RESULTS we created a myocardial ischaemia-reperfusion model in 60 C57/BL male mice to simulate an angina attack (ischaemia for 15 min, reperfusion for 1-24 h). The degree of myocardial inflammation and levels of ICAM-1 protein were determined by histological and immunohistochemical analyses. UMI with MB targeted to endothelial ICAM-1, as well as routine non-invasive methods including electrocardiography, echocardiography, and plasma troponin I levels, were utilized to evaluate ischaemia over the time course of reperfusion. Levels of ICAM-1 in the vascular endothelium were significantly increased over the time course of reperfusion (8-24 h) of the ischaemic myocardium. The video intensity of ICAM-1 molecular images of the ischaemic anterior wall was almost three times greater than that in the non-ischaemic posterior wall during the late phase (8-24 h) of reperfusion. In contrast, routine methods yielded only weak evidence of ischaemia. CONCLUSION UMI with MB targeted to endothelial ICAM-1 provides reliable evidence of a recent myocardial ischaemic event in the late phase of reperfusion.

Myocardial Hypertrophic Preconditioning Attenuates Cardiomyocyte Hypertrophy and Slows Progression to Heart Failure Through Upregulation of S100A8/A9.

Background— Transient preceding brief ischemia provides potent cardioprotection against subsequent long ischemia, termed ischemic preconditioning. Here, we hypothesized that transient short-term hypertrophic stimulation would induce the expression of hypertrophy regression genes and render the heart resistant to subsequent hypertrophic stress, and slow the progression to heart failure, as well. Methods and Results— Cardiomyocyte hypertrophy was induced in mice by either transverse aortic constriction or an infusion of phenylephrine, and in neonatal rat ventricular cardiomyocytes by norepinephrine exposures. In the preconditioning groups, hypertrophic stimulation was provided for 1 to 7 days and then withdrawn for several days by either aortic debanding or discontinuing phenylephrine or norepinephrine treatment, followed by subsequent reexposure to the hypertrophic stimulus for the same period as in the control group. One or 6 weeks after transverse aortic constriction, the heart weight/body weight ratio was lower in the preconditioning group than in the control group, whereas the lung weight/body weight ratio was significantly decreased 6 weeks after transverse aortic constriction. Similar results were obtained in mice receiving phenylephrine infusion and neonatal rat ventricular cardiomyocytes stimulated with norepinephrine. Both mRNA and protein expression of S100A8 and S100A9 showed significant upregulation after the removal of hypertrophic stimulation and persisted for 6 weeks in response to reimposition of transverse aortic constriction. The treatment with recombinant S100A8/A9 inhibited norepinephrine-induced myocyte hypertrophy and reduced the expression of calcineurin and NFATc3, but the silencing of S100A8/A9 prevented such changes. Conclusions— Preconditioning with prohypertrophic factors exerts an antihypertrophic effect and slows the progression of heart failure, indicating the existence of the phenomenon for hypertrophic preconditioning.

FGF23 promotes myocardial fibrosis in mice through activation of β-catenin

Fibroblast growth factor 23 (FGF23) has been reported to induce left ventricular hypertrophy, but it remains unclear whether FGF23 plays a role in cardiac fibrosis. This study is attempted to investigate the role of FGF23 in post-infarct myocardial fibrosis in mice. We noted that myocardial and plasma FGF23 and FGF receptor 4 were increased in mice with heart failure as well as in cultured adult mouse cardiac fibroblasts (AMCFs) exposed to angiotensin II, phenylephrine, soluble fractalkine. Recombinant FGF23 protein increased active β-catenin , procollagen I and procollagen III expression in cultured AMCFs. Furthermore, intra-myocardial injection of adeno-associated virus-FGF23 in mice significantly increased left ventricular end-diastolic pressure and myocardial fibrosis, and markedly upregulated active β-catenin, transforming growth factor β (TGF-β), procollagen I and procollagen III in both myocardial infarction (MI) and ischemia/reperfusion (IR) mice, while β-catenin inhibitor or silencing of β-catenin antagonized the FGF23-promoted myocardial fibrosis in vitro and in vivo. These findings indicate that FGF23 promotes myocardial fibrosis and exacerbates diastolic dysfunction induced by MI or IR, which is associated with the upregulation of active β-catenin and TGF-β.

Antihypertrophic effects of adiponectin on cardiomyocytes are associated with the inhibition of heparin-binding epidermal growth factor signaling

This study was aimed to investigate whether the antihypertrophic effects of adiponectin in murine hearts are associated with the modulation of HB-EGF signaling. We determined the myocardial expressions of adiponectin and adiponectin receptors, brain natriuretic peptide (BNP), and HB-EGF in normal and hypertrophied hearts of adiponectin knockout mice or wild-type mice with transverse aortic constriction (TAC). Then, we observed the effects of adiponectin on cardiac hypertrophy and HB-EGF signaling in cultured neonatal rat cardiomyocytes and whole hearts of adiponectin-null mice. The myocardial mRNA and protein expressions of adiponectin in the hypertrophied hearts were significantly downregulated, and the mRNA expression of adiponectin was inversely correlated with the heart-to-body weight ratio, BNP, and HB-EGF. The TAC-induced cardiac hypertrophy and EGF receptor (EGFR) activation in the adiponectin knockout mice were significantly greater than those in the wild-type mice. Furthermore, in vitro experiments revealed that adiponectin inhibited HB-EGF-stimulated protein synthesis, HB-EGF shedding, and EGFR phosphorylation. We conclude that the inhibition of HB-EGF mediated EGFR activation is one of the alternative mechanisms for the antihypertrophic action of adiponectin.

Cytosolic CARP Promotes Angiotensin II- or Pressure Overload-Induced Cardiomyocyte Hypertrophy through Calcineurin Accumulation

The gene ankyrin repeat domain 1 (Ankrd1) is an enigmatic gene and may exert pleiotropic function dependent on its expression level, subcellular localization and even types of pathological stress, but it remains unclear how these factors influence the fate of cardiomyocytes. Here we attempted to investigate the role of CARP on cardiomyocyte hypertrophy. In neonatal rat ventricular cardiomyocytes (NRVCs), angiotensin II (Ang II) increased the expression of both calpain 1 and CARP, and also induced cytosolic translocation of CARP, which was abrogated by a calpain inhibitor. In the presence of Ang-II in NRVCs, infection with a recombinant adenovirus containing rat Ankrd1 cDNA (Ad-Ankrd1) enhanced myocyte hypertrophy, the upregulation of atrial natriuretic peptide and β-myosin heavy chain genes and calcineurin proteins as well as nuclear translocation of nuclear factor of activated T cells. Cyclosporin A attenuated Ad-Ankrd1-enhanced cardiomyocyte hypertrophy. Intra-myocardial injection of Ad-Ankrd1 in mice with transverse aortic constriction (TAC) markedly increased the cytosolic CARP level, the heart weight/body weight ratio, while short hairpin RNA targeting Ankrd1 inhibited TAC-induced hypertrophy. The expression of calcineurin was also significantly increased in Ad-Ankrd1-infected TAC mice. Olmesartan (an Ang II receptor antagonist) prevented the upregulation of CARP in both Ang II-stimulated NRVCs and hearts with pressure overload. These findings indicate that overexpression of Ankrd1 exacerbates pathological cardiac remodeling through the enhancement of cytosolic translocation of CARP and upregulation of calcineurin.