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      Astragaloside attenuates myocardial injury in a rat model of acute myocardial infarction by upregulating hypoxia inducible factor-1α and Notch1/Jagged1 signaling

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          Abstract

          The present study aimed to investigate the mechanisms underlying the cardioprotective effect of Astragaloside against myocardial injury following myocardial infarction (MI) in a rat model. Male Wistar rats were subjected to left anterior descending branch ligation. The rats that survived 24 h (n=18) were randomly and equally assigned to three groups: MI model group, and 2.5 and 10 mg/kg/day Astragaloside group. A further six rats underwent identical surgical procedures without artery ligation, serving as sham controls. Following 28 days of treatment, the left ventricle was harvested for morphological analysis, and mRNA and protein expression levels of hypoxia inducible factor-1α (HIF-1α), Notch1 and Jagged1 were measured. Treatment with Astragaloside attenuated pathological changes in the myocardium. Compared with untreated MI rats, rats treated with Astragaloside exhibited significantly increased mRNA expression levels of HIF-1α, Notch1 and Jagged1 (all P<0.01). HIF-1α demonstrated a dose-dependent effect (P<0.05). Astragaloside (10 mg/kg/day) significantly increased HIF-1α (P<0.05), Notch1 (P<0.01) and Jagged1 (P<0.01) protein expression levels. Additionally, 2.5 mg/kg Astragaloside significantly increased Jagged1 protein expression levels compared with untreated MI rats. Furthermore, there was a dose-dependent effect of Astragaloside treatment (P<0.01). These findings suggested that the cardioprotective effects of Astragaloside against myocardial injury following MI may involve upregulation of HIF-α, Notch1 and Jagged1 signaling, implicating these molecules as therapeutic targets for the treatment of MI.

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          Most cited references29

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          Early expression of angiogenesis factors in acute myocardial ischemia and infarction.

          When the myocardium is deprived of blood, a process of ischemia, infarction, and myocardial remodeling is initiated. Hypoxia-inducible factor 1 (HIF-1) is a transcriptional activator of vascular endothelial growth factor (VEGF) and is critical for initiating early cellular responses to hypoxia. We investigated the temporal and spatial patterns of expression of the alpha subunit of HIF-1 (HIF-1alpha) and VEGF in specimens of human heart tissue to elucidate the early molecular responses to myocardial hypoxia. Ventricular-biopsy specimens from 37 patients undergoing coronary bypass surgery were collected. The specimens were examined by microscopy for evidence of ischemia, evolving infarction, or a normal histologic appearance. The specimens were also analyzed with the reverse-transcriptase polymerase chain reaction for HIF-1alpha and VEGF messenger RNA (mRNA) expression and by immunohistochemical analysis for the location of the HIF-1alpha and VEGF proteins. HIF-1alpha mRNA was detected in myocardial specimens with pathological evidence of acute ischemia (onset, <48 hours before surgery) or early infarction (onset, <24 hours before surgery). In contrast, VEGF transcripts were seen in specimens with evidence of acute ischemia or evolving infarction (onset, 24 to 120 hours before surgery). Patients with normal ventricles or evidence of infarction in the distant past had no detectable levels of either VEGF mRNA or HIF-1alpha mRNA. HIF-1alpha immunoreactivity was detected in the nuclei of myocytes and endothelial cells, whereas VEGF immunoreactivity was found in the cytoplasm of endothelial cells lining capillaries and arterioles. An increase in the level of HIF-1alpha is an early response to myocardial ischemia or infarction. This response defines, at a molecular level, one of the first adaptations of human myocardium to a deprivation of blood. HIF-1alpha is a useful temporal marker of acutely jeopardized myocardium.
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            Hypoxia-inducible factor 1-alpha reduces infarction and attenuates progression of cardiac dysfunction after myocardial infarction in the mouse.

            The aim of this research was to test whether constitutive expression of hypoxia-inducible factor 1-alpha (HIF-1alpha) influences infarction size and cardiac performance after myocardial infarction. A major question in clinical medicine is whether infarction size and border zone remodeling of the heart can be influenced by the overexpression of specific genes in the peri-infarction region. We investigated the role of constitutive HIF-1alpha expression in acute myocardial infarction using a transgenic model. Transgenic mice containing the HIF-1alpha gene under the control of the alpha-myosin heavy chain promoter were constructed. Myocardial infarction was produced by coronary ligation in HIF-1alpha transgenic mice and control animals. Extent of infarction was then quantitated by two-dimensional and M-mode echocardiography as well as by molecular and pathologic analysis of heart samples in infarct, peri-infarct, and remote heart regions at serial time points. Constitutive overexpression of HIF-1alpha in the murine heart resulted in attenuated infarct size and improved cardiac function 4 weeks after myocardial infarction. Significantly, we found an increase in both capillary density as well as vascular endothelial growth factor and inducible nitric oxide synthase expression in peri-infarct and infarct regions in the hearts of constitutive HIF-1alpha-expressing animals compared to control animals. These observations suggest the involvement of HIF-1alpha in myocardial remodeling and peri-infarct vascularization. Our results show that supranormal amounts of this peptide protect against extension of infarction and improve border zone survival in myocardial infarction.
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              Activation of Notch-mediated protective signaling in the myocardium.

              The Notch network regulates multiple cellular processes, including cell fate determination, development, differentiation, proliferation, apoptosis, and regeneration. These processes are regulated via Notch-mediated activity that involves hepatocyte growth factor (HGF)/c-Met receptor and phosphatidylinositol 3-kinase/Akt signaling cascades. The impact of HGF on Notch signaling was assessed following myocardial infarction as well as in cultured cardiomyocytes. Notch1 is activated in border zone cardiomyocytes coincident with nuclear c-Met following infarction. Intramyocardial injection of HGF enhances Notch1 and Akt activation in adult mouse myocardium. Corroborating evidence in cultured cardiomyocytes shows treatment with HGF or insulin increases levels of Notch effector Hes1 in immunoblots, whereas overexpression of activated Notch intracellular domain prompts a 3-fold increase in phosphorylated Akt. Infarcted hearts injected with adenoviral vector expressing Notch intracellular domain treatment exhibit improved hemodynamic function in comparison with control mice after 4 weeks, implicating Notch signaling in a cardioprotective role following cardiac injury. These results indicate Notch activation in cardiomyocytes is mediated through c-Met and Akt survival signaling pathways, and Notch1 signaling in turn enhances Akt activity. This mutually supportive crosstalk suggests a positive survival feedback mechanism between Notch and Akt signaling in adult myocardium following injury.
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                Author and article information

                Journal
                Mol Med Rep
                Mol Med Rep
                Molecular Medicine Reports
                D.A. Spandidos
                1791-2997
                1791-3004
                June 2017
                27 April 2017
                27 April 2017
                : 15
                : 6
                : 4015-4020
                Affiliations
                [1 ]Department of Geriatrics, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
                [2 ]Department of Geriatrics, The Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150086, P.R. China
                Author notes
                Correspondence to: Dr Yina Zhang, Department of Geriatrics, The Second Affiliated Hospital of Harbin Medical University, 246 Xuefu Road, Harbin, Heilongjiang 150086, P.R. China, E-mail: yinazhangdc@ 123456sina.com
                Article
                mmr-15-06-4015
                10.3892/mmr.2017.6522
                5436283
                28487976
                96f55609-d881-4c97-978d-1fb20967fde1
                Copyright: © Yu et al.

                This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

                History
                : 04 March 2016
                : 16 February 2017
                Categories
                Articles

                astragaloside,myocardial injury,hypoxia inducible factor 1 α,notch1,jagged1

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