Search

Background/Aims: Troxerutin, also known as vitamin P4, has been commonly used in the treatment of chronic venous insufficiency (CVI) disease. However, its effect on in vivo myocardial ischemia/reperfusion (I/R) injury, a model that closely mimics acute myocardial infarction in humans, is still unknown. Methods: The myocardial I/R injury rat model was created with troxerutin preconditioning. Myocardial infarct size was evaluated by the Evans blue-TTC method. Hemodynamic parameters, including the heart rate (HR), left ventricular end-diastolic pressure (LVEDP), left ventricular systolic pressure (LVSP), maximal rate of rise in blood pressure in the ventricular chamber (+dp/dt max), and maximal rate of decline in blood pressure in the ventricular chamber (-dp/dt max) were monitored. Serum TNF-α and IL-10 were determined by ELISA kit. Cell apoptosis was detected by MTT method. Results: Troxerutin preconditioning significantly reduced myocardial infarct size, improved cardiac function, and decreased the levels of creatine kinase (CK), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) in the I/R injury rat model. The serum and mRNA levels of TNF-α and IL-10 as well as some apoptosis markers (Bax, Caspase 3) also decreased. Moreover, troxerutin pretreatment markedly increased the phosphorylation of Akt, and blocking PI3K activity by LY294002 abolished the protective effect of troxerutin on I/R injury. Conclusion: Troxerutin preconditioning protected against myocardial I/R injury via the PI3K/Akt pathway. [ABSTRACT FROM AUTHOR]

Background: Human ether-a-go-go-related gene (HERG) channel is the major molecular component of the native rapid delayed rectifier K+ current (IKr) that is a crucial determinant of cardiac repolarization. Impairment of IKr/HERG function is commonly believed to be a mechanism causing long QT syndromes (LQTS), a lethal ventricular tachyarrhythmia. The cAMP-dependent protein kinase A (PKA) and PKC activities are markedly increased in some pathological conditions of the heart such as heart failure. This study was designed to investigate the effects of acute and chronic exposure to PKA or PKC activators and inhibitors on HERG channel activities and to provide insight into the mechanisms for the modulations. Methods: Channel activity was measured in HEK293 cells stably expressing HERG using whole-cell patch-clamp techniques. Intracellular reactive oxygen species (ROS) were measured by CM-H2DFDA. Mitochondrial membrane potential (ΔΨm) was measured using JC-1 dye. HERG channel phosphorylation was assayed by [32P]orthophosphate methods. Results: Acute exposure of cells to PKA or PKC activators by bath superfusion minimally affected IHERG, and so did the PKA or PKC inhibitor. By comparison, prolonged exposure (chronic incubation) of cells to PKA or PKC activators significantly impaired HERG K+ channel function as reflected by reduced IHERG density and positive shift of the steady-state activation curve. Antioxidants vitamin E and MnTBAP both abolished the depressive effects of PKA or PKC activators on HERG function. Further, both PKA and PKC activators stimulated production of intracellular reactive oxygen species (ROS), an effect efficiently prevented by antioxidants or by PKA and PKC inhibitors. Conclusions: HERG function is insensitive to PKA or PKC phosphorylation modulation per se, but can be impaired by the activators of PKA or PKC with long exposure likely via generation of ROS. In view of the critical role of HERG K+ channel in regulating cardiac repolarization and the sustained activation of both PKA and PKC in many pathological conditions of the heart such as heart failure, it is conceivable that HERG impairment by ROS accumulation induced by PKA and PKC contributes to the impaired cardiac repolarization. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background/Aims: Cardiac fibrosis is a major cause of diverse cardiovascular diseases. MicroRNAs have recently been proven a novel class of regulators of cardiac fibrosis. In this study, we sought to investigate the role of miR-323a-3p and its mechanisms in regulating cardiac fibrosis. Methods: The transverse aortic constriction (TAC) mice model was induced and neonatal cardiac fibroblasts (CFs) were cultured. MTT (3- [4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay was used to detect the cell viability. Echocardiography was used to evaluate cardiac function. Masson's Trichrome stain was used to evaluate the development of fibrosis. Luciferase activity assay was performed to confirm the miRNA's binding site. Real-time PCR and Western blot were used to evaluate the level of mRNA and protein. Results: MiR-323a-3p was found up-regulated in myocardial tissues subjected to TAC and in CFs cultured with Angiotensin Ⅱ (Ang Ⅱ). Overexpression of miR-323a-3p significantly increased the mRNA levels of collagen Ⅰ, collagen Ⅲ, MMP2 and MMP9, while inhibition of miR-323a-3p prevented the proliferation, collagen production and the protein level of transforming growth factor (TGF-β) in rat neonatal CFs. Strikingly, injection of antagomiR-323a-3p elevated cardiac function and inhibited the expression of TGF-β in the TAC mice. TIMP3 was a direct target of miR-323a-3p, as the overexpression of miR-323a-3p decreased the protein and mRNA levels of TIMP3. In the CFs with pre-treatment of Ang Ⅱ, siRNA-TIMP abolished the effects of AMO-323a-3p on the inhibition of the proliferation of CFs, the down-regulation of collagen Ⅰ and collagen Ⅲ, and the expression of TGF-β. Conclusion: Our findings provide evidence that miR-323a-3p promotes cardiac fibrosis via miR-323a-3p-TIMP3-TGF-β pathway. miR-323a-3p may be a new marker for cardiac fibrosis progression and that inhibition of miR-323a-3p may be a promising therapeutic target for the treatment of cardiac fibrosis. [ABSTRACT FROM AUTHOR]