ABSTRACT
OBJECTIVES: MicroRNA-7 (miR-7) is highly connected to cancerous cell proliferation and metastasis. It is also involved in myocardial ischemia-reperfusion (I/R) injury and is upregulated in cardiomyocyte under simulated I/R (SI/R). We aimed to investigate the role of miR-7 during myocardial I/R injury in vitro and in vivo and a possible gene target. METHODS AND RESULTS: Real-time PCR revealed that miR-7a/b expression was upregulated in H9c2 cells after SI/R. Flow cytometry showed SI/R-induced cell apoptosis was decreased with miR-7a/b mimic transfection but increased with miR-7a/b inhibitor in H9c2 cells. In a rat cardiac I/R injury model, infarct size determination and TUNEL assay revealed that miR-7a/b mimic decreased but miR-7a/b inhibitor increased cardiac infarct size and cardiomyocyte apoptosis as compared with controls. We previously identified an important gene connected with cell apoptosis--poly(ADP-ribose) polymerase (PARP)--as a candidate target for miR-7a/b and verified the target by luciferase reporter activity assay and western blot analysis. CONCLUSIONS: miR-7a/b is sensitive to I/R injury and protects myocardial cells against I/R-induced apoptosis by negatively regulating PARP expression in vivo and in vitro. miR-7a/b may provide a new therapeutic approach for treatment of myocardial I/R injury. Poly(ADP-ribose) polymerase.
Subject(s)
MicroRNAs/physiology , Myocytes, Cardiac/pathology , Poly(ADP-ribose) Polymerases/metabolism , Reperfusion Injury/prevention & control , Animals , Apoptosis/drug effects , Base Sequence , Cell Line , Humans , In Situ Nick-End Labeling , Myocytes, Cardiac/enzymology , Rats , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
OBJECTIVES: The aim of this study was to test the hypothesis that angiotensin (Ang)-converting enzyme-2 (ACE2) overexpression may inhibit myocardial collagen accumulation and improve left ventricular (LV) remodeling and function in diabetic cardiomyopathy. BACKGROUND: Hyperglycemia activates the renin-Ang system, which promotes the accumulation of extracellular matrix and progression of cardiac remodeling and dysfunction. METHODS: Ninety male Wistar rats were divided randomly into treatment (n = 80) and control (n = 10) groups. Diabetes was induced in the treatment group by a single intraperitoneal injection of streptozotocin. Twelve weeks after streptozotocin injection, rats in the treatment group were further divided into adenovirus-ACE2, adenovirus-enhanced green fluorescent protein, losartan, and mock groups (n = 20 each). LV volume; LV systolic and diastolic function; extent of myocardial fibrosis; protein expression levels of ACE2, Ang-converting enzyme, and Ang-(1-7); and matrix metalloproteinase-2 activity were evaluated. Cardiac myocyte and fibroblast culture was performed to assess Ang-II and collagen protein expression before and after ACE2 gene transfection. RESULTS: Four weeks after ACE2 gene transfer, the adenovirus-ACE2 group showed increased ACE2 expression, matrix metalloproteinase-2 activity, and LV ejection fractions and decreased LV volumes, myocardial fibrosis, and ACE, Ang-II, and collagen expression in comparison with the adenovirus-enhanced green fluorescent protein and control groups. ACE2 was superior to losartan in improving LV remodeling and function and reducing collagen expression. The putative mechanisms may involve a shift in balance toward an inhibited fibroblast-myocyte cross-talk for collagen and transforming growth factor-beta production and enhanced collagen degradation by matrix metalloproteinase-2. CONCLUSIONS: ACE2 inhibits myocardial collagen accumulation and improves LV remodeling and function in a rat model of diabetic cardiomyopathy. Thus, ACE2 provides a promising approach to the treatment of patients with diabetic cardiomyopathy.
Subject(s)
Diabetic Cardiomyopathies/genetics , Gene Expression Regulation , Myocardium/enzymology , Peptidyl-Dipeptidase A/genetics , RNA, Messenger/genetics , Ventricular Function, Left/physiology , Ventricular Remodeling/physiology , Angiotensin-Converting Enzyme 2 , Animals , Blotting, Western , Diabetes Mellitus, Experimental , Diabetic Cardiomyopathies/enzymology , Diabetic Cardiomyopathies/physiopathology , Echocardiography , Heart Ventricles/diagnostic imaging , Heart Ventricles/physiopathology , Immunohistochemistry , Male , Myocardium/pathology , Peptidyl-Dipeptidase A/biosynthesis , Rats , Rats, Wistar , Real-Time Polymerase Chain ReactionABSTRACT
We and others have reported that Rho-kinase plays an important role in the pathogenesis of heart ischemia/reperfusion (I/R) injury. Studies have also demonstrated that the activation of Rho-kinase is reversed in ischemic preconditioning (IPC). However, the mechanisms by which Rho-kinase is increased in I/R and reversed in IPC are not thoroughly understood. In female Wistar rats, we created I/R by ligating the left anterior-descending branch of the coronary artery (LAD) for 30 min and releasing the ligature for 180 min. IPC rats underwent IPC (two cycles of 5-min ligation of the LAD and 5-min reflow) before I/R. IPC caused a significant increase in extracellular signal-regulated kinase (ERK)1/2 activity and reduced Rho-kinase activity and cardiomyocyte apoptosis (P<0.05 versus I/R). Administration of PD98059, an inhibitor of ERK-mitogen-activated protein kinase (MAPK), increased cardiomyocyte apoptosis, Caspase-3 activity and myocardial infarction size (P<0.05 versus IPC). Western-blot analysis showed that administration of PD98059 increased Rho-kinase activity. Treatment with fasudil, an inhibitor of Rho-kinase, reversed cell apoptosis caused by treatment with PD98059 in IPC. In addition, ROCK1 (Rho-kinase 1) may be the major Rho-kinase isoform that is opposed by ERK-MAPK signaling in IPC. These results indicate that ERK-MAPK signaling is required in IPC to oppose Rho-kinase activity in cardiomyocyte apoptosis in vivo.
Subject(s)
Apoptosis/physiology , Extracellular Signal-Regulated MAP Kinases/metabolism , MAP Kinase Signaling System/physiology , Myocytes, Cardiac/enzymology , rho-Associated Kinases/metabolism , Analysis of Variance , Animals , Apoptosis/drug effects , Blotting, Western , Caspase 3/metabolism , Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors , Female , Flavonoids/pharmacology , In Situ Nick-End Labeling , Ischemic Preconditioning, Myocardial , MAP Kinase Signaling System/drug effects , Myocardial Infarction/enzymology , Myocardial Infarction/pathology , Myocardial Reperfusion Injury/enzymology , Myocardial Reperfusion Injury/pathology , Myocardial Reperfusion Injury/prevention & control , Myocytes, Cardiac/pathology , Rats , Rats, Wistar , rho-Associated Kinases/antagonists & inhibitors , rho-Associated Kinases/genetics , rhoA GTP-Binding Protein/metabolismABSTRACT
BACKGROUND: Recent studies have demonstrated that Rho-kinase has been proposed to play an important role in the pathogenesis of heart ischemia/reperfusion (I/R) injury. However, the mechanism of Rho-kinase mediated cardiomyocyte apoptosis in I/R is still not thoroughly understood. METHOD: Studies were performed with female Wistar rats. RESULTS: Ischemia followed by reperfusion caused a significant increase in Rho-kinase, c-Jun NH2-terminal kinase (JNK) and apoptosis-inducing factor (AIF) activity. Administration of fasudil, an inhibitor of Rho-kinase, decreased myocardial infarction size from 59.89+/-3.83% to 38.62+/-2.66% (P<0.05) and cell apoptosis from 32.78+/-5.1% to 17.05+/-4.2% (P<0.05). Western blot analysis showed that administration of fasudil reduced the activation of JNK and attenuated mitochondrial-nuclear translocation of AIF. Additionally, administration of SP600125, an inhibitor of JNK, attenuated mitochondrial-nuclear translocation of AIF. CONCLUSION: The inhibition of Rho-kinase reduced cell apoptosis in I/R in vivo via suppression of JNK-mediated AIF translocation.
