MicroRNAs contribute to promyelocyte apoptosis in As2O3-treated APL cells.

BACKGROUND: Arsenic trioxide (As2O3), an ancient drug used in traditional Chinese medicine, has substantial anticancer activities, especially in the treatment of patients suffering from acute promyelocytic leukemia (APL); however the underlying mechanisms are not well understood. METHODS: MTT assay was used to detect the cell viability. Flow Cytometry analysis and caspase-3 activity assay were used to measure apoptosis of APL cells. Caspase-3 and Bax levels were analyzed by western blot and let-7d and miR-766 levels were determined by real-time RT-PCR. RESULTS: As2O3 significantly inhibited cell viability and induced apoptosis in APL cells. Several microRNAs, including let-7d and miR-766, were dysregulated in APL cells treated with As2O3. The expression of caspase-3 and Bax, which are targets of let-7d and miR-766, respectively, were up-regulated in As2O3 treated cells. Transfection of let-7d and miR-766 into NB4 cells decreased the expression of caspase-3 and Bax, respectively. Correspondingly, transfection of these microRNAs increased NB4 cell viability. As2O3 induced degradation of promyelocytic leukemia (PML), and then induced the down-regulation of both let-7d and miR-766 in NB4 cells. CONCLUSIONS: We construct a dysregulated microRNA network involved in As2O3-induced apoptosis in APL. Targeting this network may be a new strategy for the prevention of side effects associated with APL treatment with As2O3.

Downregulation of miR-151-5p contributes to increased susceptibility to arrhythmogenesis during myocardial infarction with estrogen deprivation.

Estrogen deficiency is associated with increased incidence of cardiovascular diseases. But merely estrogen supplementary treatment can induce many severe complications such as breast cancer. The present study was designed to elucidate molecular mechanisms underlying increased susceptibility of arrhythmogenesis during myocardial infarction with estrogen deprivation, which provides us a new target to cure cardiac disease accompanied with estrogen deprivation. We successfully established a rat model of myocardial ischemia (MI) accompanied with estrogen deprivation by coronary artery ligation and ovariectomy (OVX). Vulnerability and mortality of ventricular arrhythmias increased in estrogen deficiency rats compared to non estrogen deficiency rats when suffered MI, which was associated with down-regulation of microRNA-151-5p (miR-151-5p). Luciferase Reporter Assay demonstrated that miR-151-5p can bind to the 3'-UTR of FXYD1 (coding gene of phospholemman, PLM) and inhibit its expression. We found that the expression of PLM was increased in (OVX+MI) group compared with MI group. More changes such as down-regulation of Kir2.1/IK1, calcium overload had emerged in (OVX+MI) group compared to MI group merely. Transfection of miR-151-5p into primary cultured myocytes decreased PLM levels and [Ca(2+)]i, however, increased Kir2.1 levels. These effects were abolished by the antisense oligonucleotides against miR-151-5p. Co-immunoprecipitation and immunofluorescent experiments confirmed the co-localization between Kir2.1 and PLM in rat ventricular tissue. We conclude that the increased ventricular arrhythmias vulnerability in response to acute myocardial ischemia in rat is critically dependent upon down-regulation of miR-151-5p. These findings support the proposal that miR-151-5p could be a potential therapeutic target for the prevention of ischemic arrhythmias in the subjects with estrogen deficiency.

Scutellarin alleviates interstitial fibrosis and cardiac dysfunction of infarct rats by inhibiting TGFß1 expression and activation of p38-MAPK and ERK1/2.

BACKGROUND AND PURPOSE: Interstitial fibrosis plays a causal role in the development of heart failure after chronic myocardial infarction (MI), and anti-fibrotic therapy represents a promising strategy to mitigate this pathological process. The purpose of this study was to investigate the effect of long-term administration of scutellarin (Scu) on cardiac interstitial fibrosis of myocardial infarct rats and the underlying mechanisms. EXPERIMENTAL APPROACH: Scu was administered to rats that were subjected to coronary artery ligation. Eight weeks later, its effects on cardiac fibrosis were assessed by examining cardiac function and histology. The number and collagen content of cultured cardiac fibroblasts exposed to angiotensin II (Ang II) were determined after the administration of Scu in vitro. Protein expression was detected by Western blot technique, and mRNA levels by quantitative reverse transcription-PCR. KEY RESULTS: The echocardiographic and haemodynamic measurements showed that Scu improved the impaired cardiac function of infarct rats and decreased interstitial fibrosis. Scu inhibited the expression of FN1 and TGFß1, but produced no effects on inflammatory cytokines (TNFα, IL-1ß and IL-6) in the 8 week infarct hearts. Scu inhibited the proliferation and collagen production of cardiac fibroblasts (CFs) and the up-regulation of FN1 and TGFß1 induced by Ang II. The enhanced phosphorylation of p38-MAPK and ERK1/2 in both infarct cardiac tissue and cultured CFs challenged by Ang II were suppressed by Scu. CONCLUSIONS AND IMPLICATIONS: Long-term administration of Scu improved the cardiac function of MI rats by inhibiting interstitial fibrosis, and the mechanisms may involve the suppression of pro-fibrotic cytokine TGFß1 expression and inhibition of p38 MAPK and ERK1/2 phosphorylation.

Scutellarin exerts its anti-hypertrophic effects via suppressing the Ca2+-mediated calcineurin and CaMKII signaling pathways.

Scutellarin is a flavonoid extracted from a traditional Chinese herb, Erigeron breviscapus Hand Mazz, which has been broadly used in treating various cardiovascular diseases. In this study, we investigated its effect on cardiac hypertrophy and the underlying mechanism. Both in vitro and in vivo cardiac hypertrophy models were employed to explore the anti-hypertrophic action of scutellarin. We found that scutellarin significantly suppressed the hypertrophic growth of neonatal cardiac myocytes exposed to phenylephrine (PE) and mouse heart subjected to pressure overload induced by aortic banding, accompanied with the decreased expression of hypertrophic markers beta-myosin heavy chain and atrial natriuretic peptide. We then measured the change of free intracellular calcium using laser scanning confocal microscope. We found that scutellarin alleviated the increment of free intracellular calcium during cardiac hypertrophy either induced by PE or aortic banding. The expression of calcium downstream effectors calcineurin and phosphorylated calmodulin kinase II (CaMKII) were significantly suppressed by scutellarin. Our study indicated that scutellarin exerts its anti-hypertrophic activity via suppressing the Ca(2+)-mediated calcineurin and CaMKII pathways, which supports the observation that clinical application of scutellarin is beneficial for cardiovascular disease patients.

Tanshinone IIA protects against sudden cardiac death induced by lethal arrhythmias via repression of microRNA-1.

BACKGROUND AND PURPOSE: Tanshinone IIA is an active component of a traditional Chinese medicine based on Salvia miltiorrhiza, which reduces sudden cardiac death by suppressing ischaemic arrhythmias. However, the mechanisms underlying the anti-arrhythmic effects remain unclear. EXPERIMENTAL APPROACH: A model of myocardial infarction (MI) in rats by ligating the left anterior descending coronary artery was used. Tanshinone IIA or quinidine was given daily, before (7 days) and after (3 months) MI; cardiac electrical activity was monitored by ECG recording. Whole-cell patch-clamp techniques were used to measure the inward rectifying K(+) current (I(K1)) in rat isolated ventricular myocytes. Kir2.1 and serum response factor (SRF) levels were analysed by Western blot and microRNA-1 (miR-1) level was determined by real-time RT-PCR. KEY RESULTS: Tanshinone IIA decreased the incidence of arrhythmias induced by acute cardiac ischaemia and mortality in rats 3 months after MI. Tanshinone IIA restored the diminished I(K1) current density and Kir2.1 protein after MI in rat ventricular myocytes, while quinidine further inhibited I(K1)/Kir2.1. MiR-1 was up-regulated in MI, possibly due to the concomitant increase in SRF, a transcriptional activator of the miR-1 gene, accounting for decreased Kir2.1. Treatment with tanshinone IIA prevented increased SRF and hence increased miR-1 post-MI, whereas quinidine did not. CONCLUSIONS AND IMPLICATIONS: Down-regulation of miR-1 and consequent recovery of Kir2.1 may account partially for the efficacy of tanshinone IIA in suppressing ischaemic arrhythmias and cardiac mortality. These finding support the proposal that miR-1 could be a potential therapeutic target for the prevention of ischaemic arrhythmias.

Scutellarin-induced endothelium-independent relaxation in rat aorta.

Scutellarin is a flavonoid extracted from the traditional Chinese herb, Erigeron breviscapus Hand Mazz. In the present study, the vasorelaxant effects of scutellarin and the underlying mechanism were investigated in isolated rat aorta. Scutellarin (3, 10, 30, 100 microm) caused a dose-dependent relaxation in both endothelium-intact and endothelium-denuded rat aortic rings precontracted with noradrenaline bitartrate (IC(50) = 7.7 +/- 0.6 microm), but not with potassium chloride. Tetraethylammonium, glibenclamide, atropine, propranolol, indomethacin and N(G)-nitro-l-arginine methyl ester had no influence on the vasorelaxant effect of scutellarin, which further excluded the involvement of potassium channels, muscarinic receptor, nitric oxide pathway and prostaglandin in this effect. Pretreatment with scutellarin decreased the tonic phase, but not the phasic phase of the noradrenaline bitartrate induced tension increment. Scutellarin also alleviated Ca(2+)-induced vasoconstriction in Ca(2+)-depleted/noradrenaline bitartrate pretreated rings in the presence of voltage-dependent calcium channel blocker verapamil. The noradrenaline bitartrate evoked intracellular calcium increase was inhibited by scutellarin. Scutellarin had no effect on phorbol-12,13-diacetate induced contraction in a calcium-free bath solution. These results showed that scutellarin could relax thoracic artery rings in an endothelium-independent manner. The mechanism seems to be the inhibition of extracellular calcium influx independent of the voltage-dependent calcium channel.

Flavonoids from Chinese Viscum coloratum produce cytoprotective effects against ischemic myocardial injuries: inhibitory effect of flavonoids on PAF-induced Ca2+ overload.

Viscum coloratum has been used in the indigenous system of medicine for the treatment of various diseases such as myocardial ischemia and arrhythmia. Platelet-activating factor (PAF) is an important player in cardiovascular diseases. The aim of this study was to investigate the protective effects of Viscum coloratum flavonoids (VCF) against ischemic myocardial injuries in vivo and to further investigate its regulatory effect on PAF. Studies were performed in a rat model of myocardial infarction and in isolated myocytes. It was found that VCF relieved myocardial injuries during ischemia. PAF (10(-11) m) significantly increased the intracellular free Ca2+ concentration ([Ca2+]i) and VCF inhibited the changes induced by PAF in single cardiac myocytes. The results suggest that VCF can improve cardiac function and that VCF reduces ischemic myocardial injuries via blocking the signaling pathway of PAF. Therefore, PAF blockers may be candidate drugs for preventing cardiac injuries during ischemia/reperfusion, and subsequently improving cardiac function.

[Effects of matrine, oxymatrine and resveratrol on HERG channel expression].

Because HERG potassium channel has important effects on both proarrhythmia and antiarrhythmia, we use immunofluorescence and Western blotting methods to detect the expression of HERG channel of HERG-HEK cells in different concentrations of matrine, oxymatrine and resveratrol. The findings showed that both matrine (1 micromol x L(-1) ) and oxymatrine ( 1micromol x L (-1) ) increased HERG channel expression ( n = 5, P < 0. 05 ) , while matrine (100 micromol x L(-1) ) decreased HERG channel expression ( n = 5, P < 0. 05), resveratrol didn't affect HERG channel expression. In conclusion, different concentrations of matrine and oxymatrine affect HERG channel expression, while there is no relationship between resveratrol and HERG channel expression. It provides a theoretical support for the safety and mechanism of anti-arrhythmic drugs.